mt76: move band capabilities in mt76_phy

[ Upstream commit 48dbce5c ]

This is a preliminary patch to move properly support mt7915 dbdc

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Stable-dep-of: 421033de ("wifi: mt76: mt7615: do not advertise 5 GHz on first phy of MT7615D (DBDC)")
Signed-off-by: Sasha Levin <sashal@kernel.org>