dma: Add lockdep asserts to virt-dma

Add lockdep asserts to all functions with "vc.lock must be held by
caller" in their documentation. This will help catch cases where these
assumptions do not hold.

Signed-off-by: Sean Anderson <[e-mail]>
Reviewed-by: Tomi Valkeinen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/virt-dma.h

···
  */
 static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
 {
+	lockdep_assert_held(&vc->lock);
+
 	list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
 	return !list_empty(&vc->desc_issued);
 }
···
 {
 	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
 	dma_cookie_t cookie;
+
+	lockdep_assert_held(&vc->lock);
 
 	cookie = vd->tx.cookie;
 	dma_cookie_complete(&vd->tx);
···
 {
 	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
 
+	lockdep_assert_held(&vc->lock);
+
 	list_add_tail(&vd->node, &vc->desc_terminated);
 
 	if (vc->cyclic == vd)
···
  */
 static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
 {
+	lockdep_assert_held(&vc->lock);
+
 	return list_first_entry_or_null(&vc->desc_issued,
 					struct virt_dma_desc, node);
 }
···
 static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
 	struct list_head *head)
 {
+	lockdep_assert_held(&vc->lock);
+
 	list_splice_tail_init(&vc->desc_allocated, head);
 	list_splice_tail_init(&vc->desc_submitted, head);
 	list_splice_tail_init(&vc->desc_issued, head);