ath9k: fix check for antenna diversity support

fixes a regression on single-stream chips introduced in
commit 43c3528430bd29f5e52438cad7cf7c0c62bf4583
"ath9k: implement .get_antenna and .set_antenna"

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Reported-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -286,7 +286,7 @@ static bool ath_complete_reset(struct ath_softc *sc, bool start)
 			ath_start_ani(common);
 	}
 
-	if (ath9k_hw_ops(ah)->antdiv_comb_conf_get && sc->ant_rx != 3) {
+	if ((ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB) && sc->ant_rx != 3) {
 		struct ath_hw_antcomb_conf div_ant_conf;
 		u8 lna_conf;