x86: consolidate header guards

This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.

Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
index c2ddd3d..71b6f7d 100644
--- a/include/asm-x86/dma-mapping.h
+++ b/include/asm-x86/dma-mapping.h
@@ -1,5 +1,5 @@
-#ifndef _ASM_DMA_MAPPING_H_
-#define _ASM_DMA_MAPPING_H_
+#ifndef ASM_X86__DMA_MAPPING_H
+#define ASM_X86__DMA_MAPPING_H
 
 /*
  * IOMMU interface. See Documentation/DMA-mapping.txt and DMA-API.txt for
@@ -233,4 +233,4 @@
 dma_mark_declared_memory_occupied(struct device *dev,
 				  dma_addr_t device_addr, size_t size);
 #endif /* CONFIG_X86_32 */
-#endif
+#endif /* ASM_X86__DMA_MAPPING_H */