qcacmn: Do vdev null check sanity before gro flush

In dp_rx_process there are two cases in which vdev will be
null. One is when peer is invalid case which happens when
packets comes on reo with out any valid peer and vdev set.
Second case is fetching more data in case of napi no yield
condition and there are no buffers to fetch. In current
dp_rx_process gro flush is called at the end of nbuff process
and with out checking for vdev sanity it is referenced. So
add vdev null sanity check to prevent NULL pointer dereference.

Change-Id: Ie2d480108118d9b83373a450aecabee57675c41d
CRs-Fixed: 2507067

dp/wifi3.0/dp_rx.c

@@ -2158,7 +2158,7 @@ done:
 				goto more_data;
 		}
 
-		if (vdev->osif_gro_flush && rx_ol_pkt_cnt) {
+		if (vdev && vdev->osif_gro_flush && rx_ol_pkt_cnt) {
 			vdev->osif_gro_flush(vdev->osif_vdev,
 					     reo_ring_num);
 		}