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/spinlock.h b/arch/x86/include/asm/spinlock.h
index 157ff7f..d17c919 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__SPINLOCK_H
-#define ASM_X86__SPINLOCK_H
+#ifndef _ASM_X86_SPINLOCK_H
+#define _ASM_X86_SPINLOCK_H
 
 #include <asm/atomic.h>
 #include <asm/rwlock.h>
@@ -361,4 +361,4 @@
 #define _raw_read_relax(lock)	cpu_relax()
 #define _raw_write_relax(lock)	cpu_relax()
 
-#endif /* ASM_X86__SPINLOCK_H */
+#endif /* _ASM_X86_SPINLOCK_H */