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/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index f43517e..f517944 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__STACKTRACE_H
-#define ASM_X86__STACKTRACE_H
+#ifndef _ASM_X86_STACKTRACE_H
+#define _ASM_X86_STACKTRACE_H
 
 extern int kstack_depth_to_print;
 
@@ -18,4 +18,4 @@
 		unsigned long *stack, unsigned long bp,
 		const struct stacktrace_ops *ops, void *data);
 
-#endif /* ASM_X86__STACKTRACE_H */
+#endif /* _ASM_X86_STACKTRACE_H */