cfg80211: fix wiphy_register error path

If rfkill_register() fails in wiphy_register() the struct device
is unregistered but everything else isn't (regulatory, debugfs)
and we even leave the wiphy instance on all internal lists even
though it will likely be freed soon, which is clearly a problem.
Fix this by cleaning up properly.

Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>