ath5k: use DECLARE_EWMA

This reduces code size slightly (at least on x86/64) while also
removing memory consumption by two unsigned long values for each
ath5k device.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wireless/ath/ath5k/Kconfig

@@ -5,7 +5,6 @@ config ATH5K
 	select MAC80211_LEDS
 	select LEDS_CLASS
 	select NEW_LEDS
-	select AVERAGE
 	select ATH5K_AHB if ATH25
 	select ATH5K_PCI if !ATH25
 	---help---