[][MAC80211][WiFi6][mt76][Add scs feature for connac2 mt76]

[Description]
Add support scs feature for connac2 codebase. This commit includes three
parts.
1. enable scs feature when interface is up.
2. support configure scs feature on/off by debugfs scs_enable.
3. Firmware needs driver to provide the tx_bytes, rx_bytes,
active_station_number, total throughtput and min rssi of all connected
stations.
In mt76 driver, we run a delayed work to send all must-need statistics
through mcu command every second.

[Release-log]
N/A

Change-Id: Iaa3e5ce3fc6124067f09d3cec7ee22e7c49b0d6a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8273217
1 file changed