x86: drop double underscores from header guards

Drop double underscores from header guards in arch/x86/include.  They
are used inconsistently, and are not necessary.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index 7c1192a..3f6000d 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -30,8 +30,8 @@
  * IN THE SOFTWARE.
  */
 
-#ifndef _ASM_X86_XEN__HYPERCALL_H
-#define _ASM_X86_XEN__HYPERCALL_H
+#ifndef _ASM_X86_XEN_HYPERCALL_H
+#define _ASM_X86_XEN_HYPERCALL_H
 
 #include <linux/errno.h>
 #include <linux/string.h>
@@ -524,4 +524,4 @@
 	mcl->args[1] = esp;
 }
 
-#endif /* _ASM_X86_XEN__HYPERCALL_H */
+#endif /* _ASM_X86_XEN_HYPERCALL_H */