aarch64: Remove AARCH64_FEATURE_F16 from AARCH64_ARCH_V8_2

The FP16 feature is optional in ARMv8.2, so it is wrong to add it to
the default AARCH64_ARCH_V8_2 feature flags.  This patch makes the
behaviour consistent with that of gcc, which also does not assume FP16
for ARMv8.2.

include/

	* opcode/aarch64.h (AARCH64_ARCH_V8_2): Drop
	AARCH64_FEATURE_F16.

include/ChangeLog

@@ -1,3 +1,8 @@
+2017-11-02  Siddhesh Poyarekar  <siddhesh@sourceware.org>
+
+	* include/opcode/aarch64.h (AARCH64_ARCH_V8_2): Drop
+	AARCH64_FEATURE_F16.
+
 2017-11-01  James Bowman  <james.bowman@ftdichip.com>
 
 	* elf/ft32.h: Add R_FT32_RELAX, SC0, SC1, DIFF32.

include/opcode/aarch64.h

@@ -70,7 +70,6 @@ typedef uint32_t aarch64_insn;
 						 | AARCH64_FEATURE_RDMA)
 #define AARCH64_ARCH_V8_2	AARCH64_FEATURE (AARCH64_ARCH_V8_1,	\
 						 AARCH64_FEATURE_V8_2	\
-						 | AARCH64_FEATURE_F16	\
 						 | AARCH64_FEATURE_RAS)
 #define AARCH64_ARCH_V8_3	AARCH64_FEATURE (AARCH64_ARCH_V8_2,	\
 						 AARCH64_FEATURE_V8_3	\