dma-mapping: remove is_device_dma_capable

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Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20190816062435.881-6-hch@lst.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/dma-mapping.h

@@ -149,11 +149,6 @@ static inline int valid_dma_direction(int dma_direction)
 		(dma_direction == DMA_FROM_DEVICE));
 }
 
-static inline int is_device_dma_capable(struct device *dev)
-{
-	return dev->dma_mask != NULL && *dev->dma_mask != DMA_MASK_NONE;
-}
-
 #ifdef CONFIG_DMA_DECLARE_COHERENT
 /*
  * These three functions are only for dma allocator.