dmaengine: imx-sdma: Remove call to memset after dma_alloc_coherent

In commit 518a2f19
("dma-mapping: zero memory returned from dma_alloc_*"),
dma_alloc_coherent has already zeroed the memory.
So memset is not needed.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Link: https://lore.kernel.org/r/20190715031716.6328-1-huangfq.daxian@gmail.com


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