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/vga.h b/arch/x86/include/asm/vga.h
index b9e493d..c4b9dc2 100644
--- a/arch/x86/include/asm/vga.h
+++ b/arch/x86/include/asm/vga.h
@@ -4,8 +4,8 @@
  *	(c) 1998 Martin Mares <mj@ucw.cz>
  */
 
-#ifndef ASM_X86__VGA_H
-#define ASM_X86__VGA_H
+#ifndef _ASM_X86_VGA_H
+#define _ASM_X86_VGA_H
 
 /*
  *	On the PC, we can just recalculate addresses and then
@@ -17,4 +17,4 @@
 #define vga_readb(x) (*(x))
 #define vga_writeb(x, y) (*(y) = (x))
 
-#endif /* ASM_X86__VGA_H */
+#endif /* _ASM_X86_VGA_H */