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 16ed0ef ("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>

Author: Olivier Dautricourt

drivers/dma/altera-msgdma.c

@@ -585,6 +585,8 @@ static void msgdma_chan_desc_cleanup(struct msgdma_device *mdev)
 	struct msgdma_sw_desc *desc, *next;
 	unsigned long irqflags;
 
+	spin_lock_irqsave(&mdev->lock, irqflags);
+
 	list_for_each_entry_safe(desc, next, &mdev->done_list, node) {
 		struct dmaengine_desc_callback cb;
 
@@ -600,6 +602,8 @@ static void msgdma_chan_desc_cleanup(struct msgdma_device *mdev)
 		/* Run any dependencies, then free the descriptor */
 		msgdma_free_descriptor(mdev, desc);
 	}
+
+	spin_unlock_irqrestore(&mdev->lock, irqflags);
 }
 
 /**
@@ -714,10 +718,11 @@ static void msgdma_tasklet(struct tasklet_struct *t)
 		}
 
 		msgdma_complete_descriptor(mdev);
-		msgdma_chan_desc_cleanup(mdev);
 	}
 
 	spin_unlock_irqrestore(&mdev->lock, flags);
+
+	msgdma_chan_desc_cleanup(mdev);
 }
 
 /**