mt76: mt7615: apply calibration-free data from OTP

MT7615 chips usually come pre-calibrated, even when used on embedded boards.
In that case, the on-flash EEPROM data needs to be merged with some data
from OTP ROM.
Run this merge if the external EEPROM data is valid and OTP has valid fields.

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