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/hpet.h b/arch/x86/include/asm/hpet.h
index 58b273f..1c22cb0 100644
--- a/arch/x86/include/asm/hpet.h
+++ b/arch/x86/include/asm/hpet.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__HPET_H
-#define ASM_X86__HPET_H
+#ifndef _ASM_X86_HPET_H
+#define _ASM_X86_HPET_H
 
 #include <linux/msi.h>
 
@@ -111,4 +111,4 @@
 #define hpet_readl(a) 0
 
 #endif
-#endif /* ASM_X86__HPET_H */
+#endif /* _ASM_X86_HPET_H */