Add get_tx_txpwr_adj function pointer to mt76_driver_ops data structure
as a preliminary patch to unify txwi configuration between mt76x0 and
mt76x2 drivers since tpc is currently supported just by mt76x2 driver
Signed-off-by: Lorenzo Bianconi <[email protected]>
Signed-off-by: Felix Fietkau <[email protected]>