dmaengine: ti: omap-dma: Remove variable override in omap_dma_tx_status()

There is no need to fetch local omap_desc since the desc we have is the
correct one already when we need to check the channel status.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20190730132029.2971-1-peter.ujfalusi@ti.com


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