RDMA/mlx4: Discard unknown SQP work requests

BugLink: https://bugs.launchpad.net/bugs/1784382

commit 6b1ca7ec upstream.

There is no need to crash the machine if unknown work request was
received in SQP MAD.

Cc: <stable@vger.kernel.org> # 3.6
Fixes: 37bfc7c1 ("IB/mlx4: SR-IOV multiplex and demultiplex MADs")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/infiniband/hw/mlx4/mad.c

@@ -1780,7 +1780,6 @@ static void mlx4_ib_sqp_comp_worker(struct work_struct *work)
 					       "buf:%lld\n", wc.wr_id);
 				break;
 			default:
-				BUG_ON(1);
 				break;
 			}
 		} else  {