ath9k_htc: Add a WMI command to get the firmware version

Also, update the wiphy information and use the correct
device pointer when registering. This would fix ethtool.

Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>