remove fenv saving/loading code from setjmp/longjmp on arm

the issue is identical to the recent commit fixing the mips versions:
despite other implementations doing this, it conflicts with the
requirements of ISO C and it's a waste of time and code size.

src/setjmp/arm/longjmp.s

@@ -21,8 +21,6 @@ longjmp:
 2:	tst r1,#0x40
 	beq 2f
 	ldc p11, cr8, [ip], #64
-	ldmia ip!, {r2,r3}
-	mcr p10, 7, r3, cr1, cr0, 0
 2:	tst r1,#0x200
 	beq 3f
 	ldcl p1, cr10, [ip], #8

src/setjmp/arm/setjmp.s

@@ -23,8 +23,6 @@ setjmp:
 2:	tst r1,#0x40
 	beq 2f
 	stc p11, cr8, [ip], #64
-	mrc p10, 7, r2, cr1, cr0, 0
-	stmia ip!, {r0,r2}
 2:	tst r1,#0x200
 	beq 3f
 	stcl p1, cr10, [ip], #8