bnxt_re: fix a crash in qp error event processing

In bnxt_qplib_process_qp_event(), for qp error events we look up the
qp-handle and pass it for further processing. But we don't check if the
handle is NULL. This could lead to a crash in the called functions when
that qp-handle is dereferenced, if the qp is destroyed in the meantime.
Fix this by checking for a valid qp-handle in that function.
Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/bnxt_re/qplib_rcfw.c

@@ -302,6 +302,8 @@ static int bnxt_qplib_process_qp_event(struct bnxt_qplib_rcfw *rcfw,
 			"QPLIB: qpid 0x%x, req_err=0x%x, resp_err=0x%x\n",
 			qp_id, err_event->req_err_state_reason,
 			err_event->res_err_state_reason);
+		if (!qp)
+			break;
 		bnxt_qplib_acquire_cq_locks(qp, &flags);
 		bnxt_qplib_mark_qp_error(qp);
 		bnxt_qplib_release_cq_locks(qp, &flags);