dmaengine: sprd: Add interrupt support for 2-stage transfer

For 2-stage transfer, some users like Audio still need transaction interrupt
to notify when the 2-stage transfer is completed. Thus we should enable
2-stage transfer interrupt to support this feature.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>