ath9k: fix channel frequency calculation for AR9340

A multiplication is missing from the current formula.

Cc: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ar9003_phy.c b/drivers/net/wireless/ath/ath9k/ar9003_phy.c
index 2df72cb..1194eeb 100644
--- a/drivers/net/wireless/ath/ath9k/ar9003_phy.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_phy.c
@@ -104,7 +104,7 @@
 			u32 chan_frac;
 
 			channelSel = (freq * 2) / 75;
-			chan_frac = ((freq % 75) * 0x20000) / 75;
+			chan_frac = (((freq * 2) % 75) * 0x20000) / 75;
 			channelSel = (channelSel << 17) | chan_frac;
 		} else {
 			channelSel = CHANSEL_5G(freq);