qcacld-3.0: Fix NULL dereference of 'vdev' in txrx

Fix dereference of pointer 'vdev' before NULL check.

Change-Id: I3d0a71f4373ae83a8642e3f2b1907c4556b114cc
CRs-Fixed: 2162245

core/dp/txrx/ol_txrx.c

@@ -5454,7 +5454,7 @@ ol_txrx_dump_pkt(qdf_nbuf_t nbuf, uint32_t nbuf_paddr, int len)
 bool
 ol_txrx_fwd_desc_thresh_check(struct ol_txrx_vdev_t *vdev)
 {
-	struct ol_tx_flow_pool_t *pool = vdev->pool;
+	struct ol_tx_flow_pool_t *pool;
 	bool enough_desc_flag;
 
 	if (!vdev)