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>
diff --git a/arch/x86/include/asm/timex.h b/arch/x86/include/asm/timex.h
index d1ce241..1287dc1 100644
--- a/arch/x86/include/asm/timex.h
+++ b/arch/x86/include/asm/timex.h
@@ -1,6 +1,6 @@
 /* x86 architecture timex specifications */
-#ifndef ASM_X86__TIMEX_H
-#define ASM_X86__TIMEX_H
+#ifndef _ASM_X86_TIMEX_H
+#define _ASM_X86_TIMEX_H
 
 #include <asm/processor.h>
 #include <asm/tsc.h>
@@ -16,4 +16,4 @@
 
 #define ARCH_HAS_READ_CURRENT_TIMER
 
-#endif /* ASM_X86__TIMEX_H */
+#endif /* _ASM_X86_TIMEX_H */