net/aeroflex: Clean ethtool_info struct assignments

If FW version is not available, it is enough to leave that field as
empty, there is no need to write N/A.

The driver version is replaced in favor of generally available
in-tree variant.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>