ath6kl: export firmware version to user space

cfg80211 exports wiphy->fw_version to user space via ethtool interface.

The obligatory screenshot:

$ sudo ethtool -i wlan0
driver: ath6kl_hifdev
version: 2.6.39-rc4+
firmware-version: 3:1:1:149
bus-info: mmc0:0001:1
$

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>