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/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
index a995f33..01fdf56 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -1,8 +1,8 @@
 /*
  * Machine dependent access functions for RTC registers.
  */
-#ifndef ASM_X86__MC146818RTC_H
-#define ASM_X86__MC146818RTC_H
+#ifndef _ASM_X86_MC146818RTC_H
+#define _ASM_X86_MC146818RTC_H
 
 #include <asm/io.h>
 #include <asm/system.h>
@@ -101,4 +101,4 @@
 
 #define RTC_IRQ 8
 
-#endif /* ASM_X86__MC146818RTC_H */
+#endif /* _ASM_X86_MC146818RTC_H */