Extend sta stats printout

Add MCS, Bandwidth, SGI, SS number, PHY type

@anjancx @janusz @Marek @slujagrz please review

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": -36,
"noise": -90,
"snr": 54,
"idle": 0,
"in_network": 1415,
"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": 1740,
"tx_total_bytes": 234865,
"tx_failures": 0,
"tx_pkts_retries": 48,
"rx_data_pkts": 32198,
"rx_data_bytes": 4179027,
"rx_failures": 3,
"rate_of_last_tx_pkt": 1300,
** "tx MCS": 9,
"tx Bandwidth": 80,
"tx SGI": 1,
"tx SS number": 3,
"tx PHY type": 9, ** "rate_of_last_rx_pkt": 1170,
** "rx MCS": 8,
"rx Bandwidth": 80,
"rx SGI": 1,
"rx SS number": 3,
"rx PHY type": 9 ** },
"rssi_per_antenna": [
-36,
-24,
-25,
-27
]
}