wifi: mt76: mt7921: move connac nic capability handling to mt7921

mt76_connac_mcu_get_nic_capability() is used by mt7921 only. It
would be better to put the code in chip folder. And we can provide
more chip capability information in mt792x_phy without making
mt76_phy much bigger.

The three functions would be moved to mt7921 folder and renamed.
mt76_connac_mcu_parse_tx_resource()
mt76_connac_mcu_parse_phy_cap()
mt76_connac_mcu_get_nic_capability()

Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>