RISC-V: Make T-Head testing pattern more generic

On some T-Head vendor extensions, we test against the constant
18446744073709551615 (2**64-1) to detect invalid immediate errors on -1.
However, it heavily depends on the fact that the value used to print
immediate value is a 64-bit unsigned type and this constant is not (and
should not be) important (we just want to know that -1 is not valid).

This commit replaces all such occurrences of 18446744073709551615 with
a more generic regular expression.

gas/ChangeLog:

	* testsuite/gas/riscv/x-thead-ba-fail.l: Replace
	18446744073709551615 with generic regular expression.
	* testsuite/gas/riscv/x-thead-bb-fail.l: Likewise.
	* testsuite/gas/riscv/x-thead-bs-fail.l: Likewise.
	* testsuite/gas/riscv/x-thead-fmemidx-fail.l: Likewise.
	* testsuite/gas/riscv/x-thead-memidx-fail.l: Likewise.
	* testsuite/gas/riscv/x-thead-mempair-fail.l: Likewise.

gas/testsuite/gas/riscv/x-thead-ba-fail.l

@@ -1,3 +1,3 @@
 .*: Assembler messages:
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)

gas/testsuite/gas/riscv/x-thead-bb-fail.l

@@ -1,7 +1,7 @@
 .*: Assembler messages:
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(64\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(32\)
 .*: Error: illegal operands `th.ext a0,64,62'
 .*: Error: illegal operands `th.extu a0,-1,0'

gas/testsuite/gas/riscv/x-thead-bs-fail.l

@@ -1,3 +1,3 @@
 .*: Assembler messages:
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(64\)

gas/testsuite/gas/riscv/x-thead-fmemidx-fail.l

@@ -1,19 +1,19 @@
 .*: Assembler messages:
 .*: Error: illegal operands `th.flrd a0,a1,a2,0'
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 

gas/testsuite/gas/riscv/x-thead-memidx-fail.l

@@ -1,14 +1,14 @@
 .*: Assembler messages:
 .*: Error: improper immediate value \(-17\)
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(16\)
 .*: Error: improper immediate value \(4\)
 
 .*: Error: illegal operands `th.ldia a0,\(a0\),0,0'
 .*: Error: illegal operands `th.ldib a0,\(a0\),0,0'
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)

gas/testsuite/gas/riscv/x-thead-mempair-fail.l

@@ -5,23 +5,23 @@
 .*: Error: illegal operands `th.sdd a0,a1,\(a2\),3'
 .*: Error: illegal operands `th.swd a0,a1,\(a2\),0'
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 .*: Error: unexpected literal \(3\)
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 .*: Error: unexpected literal \(4\)
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 .*: Error: unexpected literal \(4\)
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 .*: Error: unexpected literal \(3\)
 
-.*: Error: improper immediate value \(18446744073709551615\)
+.*: Error: improper immediate value \(-?\d+\)
 .*: Error: improper immediate value \(4\)
 .*: Error: unexpected literal \(4\)