mt76x0: antenna select corrections

Update mt76x0_phy_ant_select() to conform vendor driver, most notably
add dual antenna mode support, read configuration from EEPROM and
move ant select out of channel config to init phase. Plus small MT7630E
quirk for MT_CMB_CTRL register which vendor driver dedicated to this
chip do.

This make MT7630E workable with mt76x0e driver and do not cause any
problems on MT7610U for me.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>