mt76: mt7615: introduce mt7615_eeprom_parse_hw_band_cap routine

Introduce mt7615_eeprom_parse_hw_band_cap routine in order to configure
supported band for mt7663e and mt7622 devices since they do not rely on
eeprom data to enable 2GHz/5GHz bands

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>