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/mmconfig.h b/arch/x86/include/asm/mmconfig.h
index fb79b1c..9b119da 100644
--- a/arch/x86/include/asm/mmconfig.h
+++ b/arch/x86/include/asm/mmconfig.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__MMCONFIG_H
-#define ASM_X86__MMCONFIG_H
+#ifndef _ASM_X86_MMCONFIG_H
+#define _ASM_X86_MMCONFIG_H
 
 #ifdef CONFIG_PCI_MMCONFIG
 extern void __cpuinit fam10h_check_enable_mmcfg(void);
@@ -9,4 +9,4 @@
 static inline void check_enable_amd_mmconf_dmi(void) { }
 #endif
 
-#endif /* ASM_X86__MMCONFIG_H */
+#endif /* _ASM_X86_MMCONFIG_H */