mt76: move nl80211_dfs_regions in mt76_dev data structure

Move dfs region field in mt76_dev data structure since it is
used by all drivers. This is a preliminary patch to add DFS support to
mt7615 driver

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