UPSTREAM: dmaengine: sprd: Set request pending flag when DMA controller is active

On new Spreadtrum platforms, when the CPU enters idle, it will close
the DMA controllers' clock to save power if the DMA controller is not
busy. Moreover the DMA controller's busy signal depends on the DMA
enable flag and the request pending flag.

When DMA controller starts to transfer data, which means we already
set the DMA enable flag, but now we should also set the request pending
flag, in case the DMA clock will be closed accidentally if the CPU
can not detect the DMA controller's busy signal.

bug: 153500755
Change-Id: I9123685be01312db4caa47a742e6e6d0c8ef4e08
Signed-off-by: Zhenfang Wang <zhenfang.wang@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/02adbe4364ec436ec2c5bc8fd2386bab98edd884.1584019223.git.baolin.wang7@gmail.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>
(cherry picked from commit d0f19a48a185dab592afe1e18bf31a9d6790620d)