ath9k: Add antenna diversity tweak for CUS198

This improves RX diversity and performance for AR9485.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/init.c b/drivers/net/wireless/ath/ath9k/init.c
index abf1eb5..19b46c7 100644
--- a/drivers/net/wireless/ath/ath9k/init.c
+++ b/drivers/net/wireless/ath/ath9k/init.c
@@ -534,6 +534,7 @@
 			       ATH9K_PCI_CUS230)) {
 		ah->config.xlna_gpio = 9;
 		ah->config.xatten_margin_cfg = true;
+		ah->config.alt_mingainidx = true;
 		ah->config.ant_ctrl_comm2g_switch_enable = 0x000BBB88;
 		sc->ant_comb.low_rssi_thresh = 20;
 		sc->ant_comb.fast_div_bias = 3;