dmaengine: ep93xx: Return proper enum in ep93xx_dma_chan_direction

Clang warns when implicitly converting from one enumerated type to
another. Avoid this by using the equivalent value from the expected
type.

In file included from drivers/dma/ep93xx_dma.c:30:
./include/linux/platform_data/dma-ep93xx.h:88:10: warning: implicit
conversion from enumeration type 'enum dma_data_direction' to different
enumeration type 'enum dma_transfer_direction' [-Wenum-conversion]
                return DMA_NONE;
                ~~~~~~ ^~~~~~~~
1 warning generated.
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

include/linux/platform_data/dma-ep93xx.h

@@ -85,7 +85,7 @@ static inline enum dma_transfer_direction
 ep93xx_dma_chan_direction(struct dma_chan *chan)
 {
 	if (!ep93xx_dma_chan_is_m2p(chan))
-		return DMA_NONE;
+		return DMA_TRANS_NONE;
 
 	/* even channels are for TX, odd for RX */
 	return (chan->chan_id % 2 == 0) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM;