x86: Fix ASM_X86__ header guards

Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:

a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/auxvec.h

@@ -1,5 +1,5 @@
-#ifndef ASM_X86__AUXVEC_H
-#define ASM_X86__AUXVEC_H
+#ifndef _ASM_X86_AUXVEC_H
+#define _ASM_X86_AUXVEC_H
 /*
  * Architecture-neutral AT_ values in 0-17, leave some room
  * for more of them, start the x86-specific ones at 32.
@@ -9,4 +9,4 @@
 #endif
 #define AT_SYSINFO_EHDR		33
 
-#endif /* ASM_X86__AUXVEC_H */
+#endif /* _ASM_X86_AUXVEC_H */