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/asm.h b/arch/x86/include/asm/asm.h
index e1355f4..56be78f 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__ASM_H
-#define ASM_X86__ASM_H
+#ifndef _ASM_X86_ASM_H
+#define _ASM_X86_ASM_H
 
 #ifdef __ASSEMBLY__
 # define __ASM_FORM(x)	x
@@ -44,4 +44,4 @@
 	_ASM_PTR #from "," #to "\n" \
 	" .previous\n"
 
-#endif /* ASM_X86__ASM_H */
+#endif /* _ASM_X86_ASM_H */