Add mt7921 support ,so that we can use 6ghz.

[ss8688]

There should be less interference at 6GHz，and In my test, MT7921 only disconnects at a distance farther than RTL8812 in normal WiFi mode. I think MT7921 can also achieve a longer distance in wfb too.

[ss8688]

The Realtek WiFi 6 network card does not have open-source drivers, so I feel that the MediaTek network card is a better choice

[ss8688]

Are there any other WiFi 6 features that are beneficial for wfb？

[svpcom]

The only required feature is monitoring and injection support. Non required but very useful is support of STBC (multiple antennas TX) and LDPC (more powerful FEC than standard convolution coding). Also very useful is tx power control when doing injection.