dma-mapping: return an error code from dma_mapping_error

Currently dma_mapping_error returns a boolean as int, with 1 meaning
error.  This is rather unusual and many callers have to convert it to
errno value.  The callers are highly inconsistent with error codes
ranging from -ENOMEM over -EIO, -EINVAL and -EFAULT ranging to -EAGAIN.
Return -ENOMEM which seems to be what the largest number of callers
convert it to, and which also matches the typical error case where
we are out of resources.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/dma-mapping.h

@@ -582,7 +582,7 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 	debug_dma_mapping_error(dev, dma_addr);
 
 	if (dma_addr == DMA_MAPPING_ERROR)
-		return 1;
+		return -ENOMEM;
 	return 0;
 }