ath9k: add missing AR9340 in ath_mac_bb_names

AR9340 is not listed in ath_mac_bb_names, which leads to such a message:
ieee80211 phy0: Atheros AR???? Rev:0 mem=0xb8100000, irq=2
Signed-off-by: NFlorian Fainelli <florian@openwrt.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -2754,6 +2754,7 @@ static struct {
 	{ AR_SREV_VERSION_9271,         "9271" },
 	{ AR_SREV_VERSION_9300,         "9300" },
 	{ AR_SREV_VERSION_9330,         "9330" },
+	{ AR_SREV_VERSION_9340,		"9340" },
 	{ AR_SREV_VERSION_9485,         "9485" },
 };