qcacmn: Add support to get per chain rssi stats

Propagation from qcacld-2.0 to qcacmn.

Add support to get per chain rssi from fw through the
already existing WMI command WMI_REQUEST_STATS_CMDID
and then store it in the station_info structure defined
by cfg80211.

Change-Id: Id50c96dd322b5ca4db34cf2df901730d8b103251
CRs-Fixed: 1005367

wmi_unified_tlv.c

@@ -6157,7 +6157,7 @@ QDF_STATUS send_get_stats_cmd_tlv(wmi_unified_t wmi_handle,
 			       (wmi_request_stats_cmd_fixed_param));
 	cmd->stats_id =
 		WMI_REQUEST_PEER_STAT | WMI_REQUEST_PDEV_STAT |
-		WMI_REQUEST_VDEV_STAT;
+		WMI_REQUEST_VDEV_STAT | WMI_REQUEST_RSSI_PER_CHAIN_STAT;
 	cmd->vdev_id = get_stats_param->session_id;
 	WMI_CHAR_ARRAY_TO_MAC_ADDR(addr, &cmd->peer_macaddr);
 	WMI_LOGD("STATS REQ VDEV_ID:%d-->", cmd->vdev_id);