ath5k: fix reference clock frequency for spur mitigation on AR2413

AR2413 uses the same reference clock as AR5413

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath5k/phy.c b/drivers/net/wireless/ath/ath5k/phy.c
index acf73a0..dd2b417 100644
--- a/drivers/net/wireless/ath/ath5k/phy.c
+++ b/drivers/net/wireless/ath/ath5k/phy.c
@@ -105,6 +105,7 @@
 
 	if ((ah->ah_radio == AR5K_RF5112) ||
 	(ah->ah_radio == AR5K_RF5413) ||
+	(ah->ah_radio == AR5K_RF2413) ||
 	(ah->ah_mac_version == (AR5K_SREV_AR2417 >> 4)))
 		refclk_freq = 40;
 	else