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>
1 file changed