dmaengine: sprd: Change to use devm_platform_ioremap_resource()

Use the new helper that wraps the calls to platform_get_resource()
and devm_ioremap_resource() together, which can simpify the code.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Link: https://lore.kernel.org/r/1af3efdac3b217203cace090c8947386854c0144.1569554639.git.baolin.wang@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>