dmaengine: pl330: issue_pending waits until WFP state

According to DMA-330 errata notice[1] 71930, DMAKILL
cannot clear internal signal, named pipeline_req_active.
it makes that pl330 would wait forever in WFP state
although dma already send dma request if pl330 gets
dma request before entering WFP state.

The errata suggests that polling until entering WFP state
as workaround and then peripherals allows to issue dma request.

[1]: https://developer.arm.com/documentation/genc008428/latest

Signed-off-by: Bumyong Lee <bumyong.lee@samsung.com>
Link: https://lore.kernel.org/r/20231219055026.118695-1-bumyong.lee@samsung.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>