x86: rename the struct pt_regs members for 32/64-bit consistency

We have a lot of code which differs only by the naming of specific
members of structures that contain registers.  In order to enable
additional unifications, this patch drops the e- or r- size prefix
from the register names in struct pt_regs, and drops the x- prefixes
for segment registers on the 32-bit side.

This patch also performs the equivalent renames in some additional
places that might be candidates for unification in the future.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/vsyscall_64.c

@@ -43,7 +43,7 @@
 #include <asm/vgtod.h>
 
 #define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
-#define __syscall_clobber "r11","rcx","memory"
+#define __syscall_clobber "r11","cx","memory"
 #define __pa_vsymbol(x)			\
 	({unsigned long v;  		\
 	extern char __vsyscall_0; 	\