wifi: cfg80211: fix double lock bug in reg_wdev_chan_valid()

The locking was changed recently so now the caller holds the wiphy_lock()
lock.  Taking the lock inside the reg_wdev_chan_valid() function will
lead to a deadlock.

Fixes: f7e60032

 ("wifi: cfg80211: fix locking in regulatory disconnect")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/40c4114a-6cb4-4abf-b013-300b598aba65@moroto.mountain
Signed-off-by: Johannes Berg <johannes.berg@intel.com>