libwifi: mtk: implement wifi.backhaul.wlanX-status

struct wifi_sta is filled with sta data.
@anjancx @Marek @janusz please review

DISCONNECTED:
root@iopsys:~# ubus call wifi.backhaul.wlan1_1 status
{
"ifname": "wlan1_1",
"oper_state": "up",
"macaddr": "44:d4:37:42:48:27"
}

CONNECTED:
root@iopsys:~# ubus call wifi.backhaul.wlan1_1 status
{
"ifname": "wlan1_1",
"oper_state": "running",
"macaddr": "44:d4:37:42:48:27",
"bssid": "44:d4:37:42:3a:c7",
"frequency": "5GHz",
"rssi": -35,
"noise": -90,
"snr": 55,
"idle": 12,
"in_network": 16,
"tx_airtime": 0,
"rx_airtime": 0,
"airtime": 0,
"max_rate": 0,
"status": {
"wmm": true,
"ps": false
},
"capabilities": {
"wmm": true,
"apsd": false,
"shortslot": true,
"dot11h": false
},
"stats": {
"tx_total_pkts": 13,
"tx_total_bytes": 1334,
"tx_failures": 1,
"tx_pkts_retries": 11,
"rx_data_pkts": 344,
"rx_data_bytes": 45843,
"rx_failures": 1,
"rate_of_last_tx_pkt": 6,
"rate_of_last_rx_pkt": 6
},
"rssi_per_antenna": [
-35,
-24,
-25,
-26
]
}

Signed-off-by: Bartlomiej Grzeskowiak bartlomiej.grzeskowiak@iopsys.eu