net: fs_enet: set back promiscuity mode after restart

After interface restart (eg: after link disconnection/reconnection), the bridge
function doesn't work anymore. This is due to the promiscuous mode being cleared
by the restart.

The mac-fcc already includes code to set the promiscuous mode back during the restart.
This patch adds the same handling to mac-fec and mac-scc.

Tested with bridge function on MPC885 with FEC.

Reported-by: Germain Montoies <germain.montoies@c-s.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>