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/mmx.h b/arch/x86/include/asm/mmx.h
index 2e7299b..5cbf313 100644
--- a/arch/x86/include/asm/mmx.h
+++ b/arch/x86/include/asm/mmx.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__MMX_H
-#define ASM_X86__MMX_H
+#ifndef _ASM_X86_MMX_H
+#define _ASM_X86_MMX_H
 
 /*
  *	MMX 3Dnow! helper operations
@@ -11,4 +11,4 @@
 extern void mmx_clear_page(void *page);
 extern void mmx_copy_page(void *to, void *from);
 
-#endif /* ASM_X86__MMX_H */
+#endif /* _ASM_X86_MMX_H */