dmaengine: dw-edma: Fix to change for continuous transfer

[ Upstream commit a251994a ]

The dw-edma driver stops after processing a DMA request even if a request
remains in the issued queue, which is not the expected behavior. The DMA
engine API requires continuous processing.

Add a trigger to start after one processing finished if there are requests
remain.

Fixes: e63d79d1

 ("dmaengine: Add Synopsys eDMA IP core driver")
Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
Link: https://lore.kernel.org/r/20230411101758.438472-1-mie@igel.co.jp
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>