dmaengine: fsl-dpaa2-qdma: Adding shutdown hook

We need to ensure DMA engine could be stopped in order for kexec
to start the next kernel.
So add the shutdown operation support.

Signed-off-by: Peng Ma <peng.ma@nxp.com>
Link: https://lore.kernel.org/r/20200227042841.18358-1-peng.ma@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>