ath9k: enable support for AR9100

Because we have support for the AR9100 devices now, we can enable them.

Changes-licensed-under: ISC

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Tested-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>