dmaengine: hsu: set HSU_CH_MTSR to memory width

HSU_CH_MTSR register should be programmed to a minimum size to transfer. This
size on a memory side of the transfer. Program it accordingly.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>