mwifiex: set fw api info for backword compatibility

If we dont set FW API info here, for older FW releases where FW API
is not available in GET_HW_SPEC, API version would remain 0.
This may cause issues with 11ac if older FW is used with newer driver.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>