mwl8k: add API version checking for AP firmware

The AP firmware specifies an API version in the GET_HW_SPEC
command response.  Currently, the driver only supports AP
firmware for the 8366, and only supports API v1.  In the future,
if higher API version firmwares emerge (possibly for different
chips), different ops can be selected based on the reported API
version.

Signed-off-by: Brian Cavagnolo <brian@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>