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/scatterlist.h b/arch/x86/include/asm/scatterlist.h
index ee48f88..263d397 100644
--- a/arch/x86/include/asm/scatterlist.h
+++ b/arch/x86/include/asm/scatterlist.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__SCATTERLIST_H
-#define ASM_X86__SCATTERLIST_H
+#ifndef _ASM_X86_SCATTERLIST_H
+#define _ASM_X86_SCATTERLIST_H
 
 #include <asm/types.h>
 
@@ -30,4 +30,4 @@
 # define sg_dma_len(sg)		((sg)->dma_length)
 #endif
 
-#endif /* ASM_X86__SCATTERLIST_H */
+#endif /* _ASM_X86_SCATTERLIST_H */