ath9k_hw: add support for GPIO differences on AR9003

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index a55db3b..6f7faf0 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -3440,7 +3440,9 @@
 	if (gpio >= ah->caps.num_gpio_pins)
 		return 0xffffffff;
 
-	if (AR_SREV_9271(ah))
+	if (AR_SREV_9300_20_OR_LATER(ah))
+		return MS_REG_READ(AR9300, gpio) != 0;
+	else if (AR_SREV_9271(ah))
 		return MS_REG_READ(AR9271, gpio) != 0;
 	else if (AR_SREV_9287_10_OR_LATER(ah))
 		return MS_REG_READ(AR9287, gpio) != 0;