dmaengine: omap-dma: Add support for memcpy

The sDMA controller is capable of performing memory copy operation. It need
to be configured to software triggered mode and without HW synchronization.
The sDMA can copy data which is aligned to 8, 16 or 32 bits.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>