Some ar9344-based devices are using ath9k_patch_fw_mac_crc, which
is meant to generate a checksum, for fixing their ath9k MAC
addresses.
However, those do not have a checksum field, and the calculated
checksum offset would be negative.
This patch will use ath9k_patch_fw_mac function for those devices.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>