qcacmn: Validate rx return_buffer_manager

Host rx return_buffer_manager should always be 4 or 6. Add check for
invalid return_buffer_manager value in ring descriptor.

Change-Id: I509dd58ddd89e6a0ce1bffa509dcfabbd0fbc975
CRs-Fixed: 2632372

dp/wifi3.0/dp_stats.c

@@ -5531,6 +5531,8 @@ void dp_txrx_path_stats(struct dp_soc *soc)
 			       pdev->soc->stats.rx.err.defrag_peer_uninit);
 		DP_PRINT_STATS("pkts delivered no peer %u",
 			       pdev->soc->stats.rx.err.pkt_delivered_no_peer);
+		DP_PRINT_STATS("RX invalid cookie: %d",
+			       soc->stats.rx.err.invalid_cookie);
 
 		DP_PRINT_STATS("Reo Statistics");
 		DP_PRINT_STATS("near_full: %u ", soc->stats.rx.near_full);