mt76: mt76_connac: move pm data struct in mt76_connac.h

Move pm mt7663 data structure in mt76_connac.h introducing
mt76_connac_pm data struct. This is a preliminary patch to share pm code
between mt7663 and mt7921

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