x86: sigframe.h: add guard macro

Impact: cleanup

Add missing guard macro _ASM_X86_SIGFRAME_H.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/sigframe.h b/arch/x86/include/asm/sigframe.h
index 491a087..3bd0f42 100644
--- a/arch/x86/include/asm/sigframe.h
+++ b/arch/x86/include/asm/sigframe.h
@@ -1,3 +1,6 @@
+#ifndef _ASM_X86_SIGFRAME_H
+#define _ASM_X86_SIGFRAME_H
+
 #ifdef CONFIG_X86_32
 #define sigframe_ia32		sigframe
 #define rt_sigframe_ia32	rt_sigframe
@@ -59,3 +62,5 @@
 	/* fp state follows here */
 };
 #endif /* CONFIG_X86_64 */
+
+#endif /* _ASM_X86_SIGFRAME_H */