dmaengine: at_hdmac: fix buffer transfer size specification

Buffer transfer size is the number of transfers to be performed in
relation with the width of the _source_ interface.
So in the DMA_FROM_DEVICE case, it should be the register width that
should be taken into account.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/at_hdmac.c

@@ -722,7 +722,7 @@ atc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			desc->lli.daddr = mem;
 			desc->lli.ctrla = ctrla
 					| ATC_DST_WIDTH(mem_width)
-					| len >> mem_width;
+					| len >> reg_width;
 			desc->lli.ctrlb = ctrlb;
 
 			if (!first) {