mlxsw: core_linecards: Expose device FW version over device info

Extend MDDQ to obtain FW version of line card device and implement
device_info_get() op to fill up the info with that.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>