wifi: mt76: connac: introduce mt76_connac_reg_map structure

Introduce mt76_connac_reg_map structure in mt76-connac module since it
is used by all connac2 chipset. Align structure definitions.
This is a preliminary patch to add mt7990 chipset support.

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