IB/rxe: Prevent from completer to operate on non valid QP

On UD QP completer tasklet is scheduled for each packet sent.

If it is followed by a destroy_qp(), the kernel panic will
happen as the completer tries to operate on a destroyed QP.

Fixes: 8700e3e7c4 ("Soft RoCE driver")
Signed-off-by: Yonatan Cohen <yonatanc@mellanox.com>
Reviewed-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/sw/rxe/rxe_qp.c

@@ -813,8 +813,7 @@ void rxe_qp_destroy(struct rxe_qp *qp)
 	del_timer_sync(&qp->rnr_nak_timer);
 
 	rxe_cleanup_task(&qp->req.task);
-	if (qp_type(qp) == IB_QPT_RC)
-		rxe_cleanup_task(&qp->comp.task);
+	rxe_cleanup_task(&qp->comp.task);
 
 	/* flush out any receive wr's or pending requests */
 	__rxe_do_task(&qp->req.task);