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.h b/arch/x86/include/asm/fixmap.h
index 78e33a1..8668a94 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__FIXMAP_H
-#define ASM_X86__FIXMAP_H
+#ifndef _ASM_X86_FIXMAP_H
+#define _ASM_X86_FIXMAP_H
 
 #ifdef CONFIG_X86_32
 # include "fixmap_32.h"
@@ -65,4 +65,4 @@
 	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 	return __virt_to_fix(vaddr);
 }
-#endif /* ASM_X86__FIXMAP_H */
+#endif /* _ASM_X86_FIXMAP_H */