ath9k_hw: Initialize 2GHz CTL properly.

The last 2GHz CTL was not being initialized, so power was being
set to 0 instead of 30dbm. Initialize to 30 like other CTLs.

Signed-off-by: Senthil Balasubramanian <senthilkumar@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>