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/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 445a247..ff60551 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -30,8 +30,8 @@
  * IN THE SOFTWARE.
  */
 
-#ifndef ASM_X86__XEN__HYPERVISOR_H
-#define ASM_X86__XEN__HYPERVISOR_H
+#ifndef _ASM_X86_XEN__HYPERVISOR_H
+#define _ASM_X86_XEN__HYPERVISOR_H
 
 #include <linux/types.h>
 #include <linux/kernel.h>
@@ -79,4 +79,4 @@
 #define xen_initial_domain()	(xen_pv_domain() && xen_start_info->flags & SIF_INITDOMAIN)
 #define xen_hvm_domain()	(xen_domain_type == XEN_HVM_DOMAIN)
 
-#endif /* ASM_X86__XEN__HYPERVISOR_H */
+#endif /* _ASM_X86_XEN__HYPERVISOR_H */