wifi: cfg80211: hold wiphy lock when sending wiphy

Sending the wiphy out might cause calls to the driver,
notably get_txq_stats() and get_antenna(). These aren't
very important, since the normally have their own locks
and/or just send out static data, but if the contract
should be that the wiphy lock is always held, these are
also affected. Fix that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>