drivers/net/vsc9953: Add default configuration for VSC9953 L2 Switch

drivers/net/vsc9953: Add default configuration for VSC9953 L2 Switch

At startup, the default configuration should be:
 - enable HW learning on all ports (HW default);
 - all ports are VLAN aware;
 - all ports are members of VLAN 1;
 - all ports have Port-based VLAN 1;
 - on all ports, the switch is allowed to remove
   maximum one VLAN tag,
 - on egress, the switch should add a VLAN tag if the
   frame is classified to a different VLAN than the port's
   Port-based VLAN;

Signed-off-by: Johnson Leung <[email protected]>
Signed-off-by: Codrin Ciubotariu <[email protected]>
Acked-by: Joe Hershberger <[email protected]>
Reviewed-by: York Sun <[email protected]>