headers/x86[_64]: Name the "mxcsr_mask" fields properly.

These values aren't referenced anywhere at present however.

Change-Id: I870d6321c6d30f850f48f811213124276543a1a8
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9091
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>
Reviewed-by: Jérôme Duval <[email protected]>

headers/posix/arch/x86/signal.h

@@ -114,7 +114,7 @@ typedef struct new_extended_regs {
 	unsigned short	fp_ds;
 	unsigned short	_reserved_22_23;
 	unsigned long	mxcsr;
-	unsigned long	_reserved_28_31;
+	unsigned long	mxcsr_mask;
 	union {
 		fp_stack fp;
 		mmx_regs mmx;

headers/posix/arch/x86_64/signal.h

@@ -31,7 +31,7 @@ struct fpu_state {
 	unsigned long		rip;
 	unsigned long		rdp;
 	unsigned int		mxcsr;
-	unsigned int		mscsr_mask;
+	unsigned int		mxcsr_mask;
 
 	union {
 		struct x86_64_fp_register fp[8];