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/time.h b/arch/x86/include/asm/time.h
index 3e724ee..50c733a 100644
--- a/arch/x86/include/asm/time.h
+++ b/arch/x86/include/asm/time.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__TIME_H
-#define ASM_X86__TIME_H
+#ifndef _ASM_X86_TIME_H
+#define _ASM_X86_TIME_H
 
 extern void hpet_time_init(void);
 
@@ -60,4 +60,4 @@
 
 extern unsigned long __init calibrate_cpu(void);
 
-#endif /* ASM_X86__TIME_H */
+#endif /* _ASM_X86_TIME_H */