dmaengine: altera-msgdma: cleanup after completing all descriptors

msgdma_chan_desc_cleanup iterates the done list for each completed
descriptor while we need to do it once after all descriptors are
completed.

This fixes a Sparse warning because we first take the lock in
msgdma_tasklet.
- Move locking to msgdma_chan_desc_cleanup.
- Move call to msgdma_chan_desc_cleanup outside of the critical section of
msgdma_tasklet.

Inspired by: commit 16ed0ef3 ("dmaengine: zynqmp_dma: cleanup after
                                   completing all descriptors")

Signed-off-by: Olivier Dautricourt <olivierdautricourt@gmail.com>
Tested-by: Olivier Dautricourt <olivierdautricourt@gmail.com>
Suggested-by: Eric Schwarz <eas@sw-optimization.com>
Link: https://lore.kernel.org/r/20240608213216.25087-2-olivierdautricourt@gmail.com


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