dma-mapping: take dma_pfn_offset into account in dma_max_pfn

This makes sure the generic version can be used with architectures /
devices that have a DMA offset in the direct mapping.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

include/linux/dma-mapping.h

@@ -692,7 +692,7 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
 #ifndef dma_max_pfn
 static inline unsigned long dma_max_pfn(struct device *dev)
 {
-	return *dev->dma_mask >> PAGE_SHIFT;
+	return (*dev->dma_mask >> PAGE_SHIFT) + dev->dma_pfn_offset;
 }
 #endif