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/fixmap_32.h b/arch/x86/include/asm/fixmap_32.h
index 8844002..09f29ab 100644
--- a/arch/x86/include/asm/fixmap_32.h
+++ b/arch/x86/include/asm/fixmap_32.h
@@ -10,8 +10,8 @@
  * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
  */
 
-#ifndef ASM_X86__FIXMAP_32_H
-#define ASM_X86__FIXMAP_32_H
+#ifndef _ASM_X86_FIXMAP_32_H
+#define _ASM_X86_FIXMAP_32_H
 
 
 /* used by vmalloc.c, vsyscall.lds.S.
@@ -120,4 +120,4 @@
 #define FIXADDR_BOOT_START	(FIXADDR_TOP - __FIXADDR_BOOT_SIZE)
 
 #endif /* !__ASSEMBLY__ */
-#endif /* ASM_X86__FIXMAP_32_H */
+#endif /* _ASM_X86_FIXMAP_32_H */