RDMA/vmw_pvrdma: Use refcount_dec_and_test to avoid warning

refcount_dec generates a warning when the operation
causes the refcount to hit zero. Avoid this by using
refcount_dec_and_test.

Fixes: 8b10ba78 ("RDMA/vmw_pvrdma: Add shared receive queue support")
Reviewed-by: NAdit Ranadive <aditr@vmware.com>
Reviewed-by: NAditya Sarwade <asarwade@vmware.com>
Reviewed-by: NJorgen Hansen <jhansen@vmware.com>
Signed-off-by: NBryan Tan <bryantan@vmware.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/vmw_pvrdma/pvrdma_srq.c

@@ -236,8 +236,8 @@ static void pvrdma_free_srq(struct pvrdma_dev *dev, struct pvrdma_srq *srq)
 	dev->srq_tbl[srq->srq_handle] = NULL;
 	spin_unlock_irqrestore(&dev->srq_tbl_lock, flags);
 
-	refcount_dec(&srq->refcnt);
-	wait_event(srq->wait, !refcount_read(&srq->refcnt));
+	if (!refcount_dec_and_test(&srq->refcnt))
+		wait_event(srq->wait, !refcount_read(&srq->refcnt));
 
 	/* There is no support for kernel clients, so this is safe. */
 	ib_umem_release(srq->umem);