dmaengine: sh: fix some NULL dereferences

The dma_free_coherent() function needs a valid device pointer or it will
crash.

Fixes: 550c591a89a1 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20210827085410.GA9183@kili


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