mlxsw: spectrum_switchdev: Pass 'struct mlxsw_sp' to mlxsw_sp_bridge_mdb_mc_enable_sync()

Currently the above mentioned function gets 'struct mlxsw_sp_port',
while the only use of this structure is to get 'mlxsw_sp_port->mlxsw_sp'.

Instead, pass 'struct mlxsw_sp'.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>