ath9k_hw: Fix multicast search for AR9002 family

The multicast search bit is disabled for the AR9003
family, but this is required for AR9002 too. Fix this in
the INI override routine.

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