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/ftrace.h b/arch/x86/include/asm/ftrace.h
index 1bb6f9bb..47f7e65 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__FTRACE_H
-#define ASM_X86__FTRACE_H
+#ifndef _ASM_X86_FTRACE_H
+#define _ASM_X86_FTRACE_H
 
 #ifdef CONFIG_FTRACE
 #define MCOUNT_ADDR		((long)(mcount))
@@ -21,4 +21,4 @@
 
 #endif /* CONFIG_FTRACE */
 
-#endif /* ASM_X86__FTRACE_H */
+#endif /* _ASM_X86_FTRACE_H */