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/xor_64.h b/arch/x86/include/asm/xor_64.h
index 2d3a18d..1549b5e 100644
--- a/arch/x86/include/asm/xor_64.h
+++ b/arch/x86/include/asm/xor_64.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__XOR_64_H
-#define ASM_X86__XOR_64_H
+#ifndef _ASM_X86_XOR_64_H
+#define _ASM_X86_XOR_64_H
 
 /*
  * Optimized RAID-5 checksumming functions for MMX and SSE.
@@ -358,4 +358,4 @@
    deals with a load to a line that is being prefetched.  */
 #define XOR_SELECT_TEMPLATE(FASTEST) (&xor_block_sse)
 
-#endif /* ASM_X86__XOR_64_H */
+#endif /* _ASM_X86_XOR_64_H */