ath: map TH to FCC3_WORLD

TH gets 5 GHz.

Cc: David Quan <david.quan@atheros.com>
Cc: Michael Green <michael.green@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>