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/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index dcd4682..d0983d2 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -1,5 +1,5 @@
-#ifndef ASM_X86__VSYSCALL_H
-#define ASM_X86__VSYSCALL_H
+#ifndef _ASM_X86_VSYSCALL_H
+#define _ASM_X86_VSYSCALL_H
 
 enum vsyscall_num {
 	__NR_vgettimeofday,
@@ -41,4 +41,4 @@
 
 #endif /* __KERNEL__ */
 
-#endif /* ASM_X86__VSYSCALL_H */
+#endif /* _ASM_X86_VSYSCALL_H */