mlxsw: core: remove unnecessary function mlxsw_core_driver_put

The function mlxsw_core_driver_put only traverse mlxsw_core_driver_list
to find the matched mlxsw_driver,but never used it.
So it can be removed safely.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>