ath9k_hw: fix 5 GHz frequency selection on AR934x/AR955x with 25 MHz refclock

The old code was an accidental copy&paste of the 2.4 GHz version,
which doesn't work.
Signed-off-by: NFelix Fietkau <nbd@openwrt.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ar9003_phy.c

@@ -117,8 +117,8 @@ static int ar9003_hw_set_channel(struct ath_hw *ah, struct ath9k_channel *chan)
 		    ah->is_clk_25mhz) {
 			u32 chan_frac;
 
-			channelSel = (freq * 2) / 75;
-			chan_frac = (((freq * 2) % 75) * 0x20000) / 75;
+			channelSel = freq / 75;
+			chan_frac = ((freq % 75) * 0x20000) / 75;
 			channelSel = (channelSel << 17) | chan_frac;
 		} else {
 			channelSel = CHANSEL_5G(freq);