dmaengine: add DMA_TRANS_NONE to dma_transfer_direction

Before dma_transfer_direction was introduced to replace
dma_data_direction, some dmaengine device uses DMA_NONE of
dma_data_direction for some talk with its client drivers.
The mxs-dma and its clients mxs-mmc and gpmi-nand are such case.

This patch adds DMA_TRANS_NONE to dma_transfer_direction and
migrate the DMA_NONE use in mxs-dma to it.

It also fixes the compile warning below.

CC      drivers/dma/mxs-dma.o
drivers/dma/mxs-dma.c: In function ‘mxs_dma_prep_slave_sg’:
drivers/dma/mxs-dma.c:420:16: warning: comparison between ‘enum dma_transfer_direction’ and ‘enum dma_data_direction’
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/mxs-dma.c

@@ -391,7 +391,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
 		idx = 0;
 	}
 
-	if (direction == DMA_NONE) {
+	if (direction == DMA_TRANS_NONE) {
 		ccw = &mxs_chan->ccw[idx++];
 		pio = (u32 *) sgl;
 

include/linux/dmaengine.h

@@ -88,6 +88,7 @@ enum dma_transfer_direction {
 	DMA_MEM_TO_DEV,
 	DMA_DEV_TO_MEM,
 	DMA_DEV_TO_DEV,
+	DMA_TRANS_NONE,
 };
 
 /**