cfg80211: fix locking

Add missing unlocking of the wiphy in set_channel,
and don't try to unlock a non-existing wiphy in
set_cqm.

Cc: stable@kernel.org [2.6.35+]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>