mt76x2: dfs: take into account dfs region in mt76x2_dfs_init_params()

Do not enable DFS state machine if dfs region is set to NL80211_DFS_UNSET

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>