[PATCH] trivial: use page_to_phys in dma_map_page()

From: Trivial Patch Monkey <trivial@rustcorp.com.au>

From:  Adam Lackorzynski <adam@os.inf.tu-dresden.de>

dma_map_page() can be simplified by using page_to_phys instead of writing the
calculation explicitly.

include/asm-i386/dma-mapping.h

@@ -51,7 +51,7 @@ dma_map_page(struct device *dev, struct page *page, unsigned long offset,
 	     size_t size, enum dma_data_direction direction)
 {
 	BUG_ON(direction == DMA_NONE);
-	return (dma_addr_t)(page_to_pfn(page)) * PAGE_SIZE + offset;
+	return page_to_phys(page) + offset;
 }
 
 static inline void