dmaengine: imx-sdma: remove unused variable

The variable is no longer used, though it is set, so remove it

drivers/dma/imx-sdma.c:1298:6:
	warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]
  int ret, i, count;
      ^~~

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