first batch of mt76 patches for 4.21

* use the same firmware for mt76x2e and mt76x2u
* mt76x2 fixes
* mt76x0 fixes
* mt76x0e survey support
* more unification between mt76x2 and mt76x0
* mt76x0e AP mode support
* mt76x0e DFS support
* rework and fix tx status handling for mt76x0 and mt76x2

kvalo: fixed a conflict in drivers/net/wireless/mediatek/mt76/mt76x2/pci_main.c
and a build problem in drivers/net/wireless/mediatek/mt76/mt76x02_util.c