net: dsa: sja1105: allow VLAN configuration from the bridge in all states

Let the DSA core call our .port_vlan_add methods every time the bridge
layer requests so. We will deal internally with saving/restoring VLANs
depending on our VLAN awareness state.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>