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/cache.h b/arch/x86/include/asm/cache.h
index ea3f1cc..5d367ca 100644
--- a/arch/x86/include/asm/cache.h
+++ b/arch/x86/include/asm/cache.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__CACHE_H
-#define ASM_X86__CACHE_H
+#ifndef _ASM_X86_CACHE_H
+#define _ASM_X86_CACHE_H
 
 /* L1 cache line size */
 #define L1_CACHE_SHIFT	(CONFIG_X86_L1_CACHE_SHIFT)
@@ -17,4 +17,4 @@
 #endif
 #endif
 
-#endif /* ASM_X86__CACHE_H */
+#endif /* _ASM_X86_CACHE_H */