mlxsw: i2c: Extend initialization with querying firmware info

Extend initialization flow with query request for firmware info in
order to obtain firmware version info.
This info is to be provided to minimal driver to support ethtool
get_drvinfo() interface.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>