ath5k: initialize common->clockrate

Fixes a division by zero when setting distance before activating the
device for the first time.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
index 3e5e9b7..523bb08 100644
--- a/drivers/net/wireless/ath/ath5k/base.c
+++ b/drivers/net/wireless/ath/ath5k/base.c
@@ -2420,6 +2420,7 @@
 	common->ah = sc->ah;
 	common->hw = hw;
 	common->priv = sc;
+	common->clockrate = 40;
 
 	/*
 	 * Cache line size is used to size and align various