ath9k: move common regulatory code out of if() branches

Both branches of the regulatory check in ath_attach() set up a
custom regulatory domain and apply radar and world flags, so extract
those into a single path.

While at it, fix a couple of spelling errors and an unnecessary extra
pointer traversal.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Acked-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>