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>

arch/x86/include/asm/device.h

@@ -1,5 +1,5 @@
-#ifndef ASM_X86__DEVICE_H
-#define ASM_X86__DEVICE_H
+#ifndef _ASM_X86_DEVICE_H
+#define _ASM_X86_DEVICE_H
 
 struct dev_archdata {
 #ifdef CONFIG_ACPI
@@ -13,4 +13,4 @@ struct dma_mapping_ops *dma_ops;
 #endif
 };
 
-#endif /* ASM_X86__DEVICE_H */
+#endif /* _ASM_X86_DEVICE_H */