dmaengine: ti: k3-udma: Add missing dma_sync call for rx flush descriptor

The TR mode rx flush descriptor did not had a dma_sync_single_for_device()
call to make sure that the DMA see the correct information.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200512134544.5839-1-peter.ujfalusi@ti.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>