i.MX SDMA: Fix burstsize settings

Commit 6584cb88 (ARM i.MX dma: Fix burstsize settings) fixed
the mxcmmc driver but forgot to fix the SDMA driver to handle the
correct burtsize.
This make the SD card access works again with DMA on i.MX31 boards.

Signed-off-by: Philippe Rétornaz <philippe.retornaz@epfl.ch>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>