dmaengine: ptdma: handle the cases based on DMA is complete

There is a need to segregate the cases when DMA is complete or not.
In case if DMA is already complete there is no need to handle it
again and gracefully exit from the function.

Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Link: https://lore.kernel.org/r/1643814880-3882-3-git-send-email-Sanju.Mehta@amd.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>