libertas: don't blindly try mesh

The CF card only has a very old firmware (5.0.16p0). This firmware doesn't
know anything about mesh config. However, current code blindly calls
mesh_config when the card is inserted. So check the firmware version before
issuing this command.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>