dmaengine: imx-sdma: pass ->dev to dma_alloc_coherent() API

Pass ->dev to dma_alloc_coherent() API. We need this
because dma_alloc_coherent() makes use of dev parameter
and receiving NULL will result in a crash.

Signed-off-by: Andy Duan <fugang.duan@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>