dmaengine: at_xdmac: fix at_xdmac_prep_dma_memcpy()

This patch fixes at_xdmac_prep_dma_memcpy(). Indeed the data width field
of the Channel Configuration register was not updated properly in the
loop: the bits of the dwidth field were not cleared before adding their
new value.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Fixes: e1f7c9eee70 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Cc: stable@vger.kernel.org #4.1 and later
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/at_xdmac.c

@@ -1088,6 +1088,7 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 		/* Check remaining length and change data width if needed. */
 		dwidth = at_xdmac_align_width(chan,
 					      src_addr | dst_addr | xfer_size);
+		chan_cc &= ~AT_XDMAC_CC_DWIDTH_MASK;
 		chan_cc |= AT_XDMAC_CC_DWIDTH(dwidth);
 
 		ublen = xfer_size >> dwidth;