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/vdso.h b/arch/x86/include/asm/vdso.h
index 4ab3209..9064052 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__VDSO_H
-#define ASM_X86__VDSO_H
+#ifndef _ASM_X86_VDSO_H
+#define _ASM_X86_VDSO_H
 
 #ifdef CONFIG_X86_64
 extern const char VDSO64_PRELINK[];
@@ -44,4 +44,4 @@
 extern const char vdso32_syscall_start, vdso32_syscall_end;
 extern const char vdso32_sysenter_start, vdso32_sysenter_end;
 
-#endif /* ASM_X86__VDSO_H */
+#endif /* _ASM_X86_VDSO_H */