net: dsa: sja1105: manage VLANs on cascade ports

Since commit ed040abc ("net: dsa: sja1105: use 4095 as the private
VLAN for untagged traffic"), this driver uses a reserved value as pvid
for the host port (DSA CPU port). Control packets which are sent as
untagged get classified to this VLAN, and all ports are members of it
(this is to be expected for control packets).

Manage all cascade ports in the same way and allow control packets to
egress everywhere.

Also, all VLANs need to be sent as egress-tagged on all cascade ports.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>