dmaengine: fsl-dpaa2-qdma: remove set but not used variable 'dpaa2_qdma'

drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c: In function dpaa2_qdma_shutdown:
drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c:795:28: warning: variable dpaa2_qdma set but not used [-Wunused-but-set-variable]

commit 3e0ca3c3

 ("dmaengine: fsl-dpaa2-qdma: Adding shutdown hook")
involved this, remove it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200303131347.28392-1-yuehaibing@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>