ath9k: Modify IDs to identify CUS230

CUS198 and CUS230 are similar cards, both
are AR9485 + xLNA solutions. But, the subsystem IDs
differ - identify CUS230 explicitly to make things
clearer.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>