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/mtrr.h b/arch/x86/include/asm/mtrr.h
index 23a7f83..7c1e425 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -20,8 +20,8 @@
     The postal address is:
       Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
 */
-#ifndef ASM_X86__MTRR_H
-#define ASM_X86__MTRR_H
+#ifndef _ASM_X86_MTRR_H
+#define _ASM_X86_MTRR_H
 
 #include <linux/ioctl.h>
 #include <linux/errno.h>
@@ -170,4 +170,4 @@
 
 #endif /* __KERNEL__ */
 
-#endif /* ASM_X86__MTRR_H */
+#endif /* _ASM_X86_MTRR_H */