ath9k: fix custom regulatory call position

ath_regd_init() needs to be called with the wiphy already
properly set with the bands. Without this the custom regulatory
settings were not taking effect, and the device would get
the default channel settings from ath9k_[25]ghz_chantable.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>