net: dsa: sja1105: add packing ops for the Retagging Table

The Retagging Table is an optional feature that allows the switch to
match frames against a {ingress port, egress port, vid} rule and change
their VLAN ID. The retagged frames are by default clones of the original
ones (since the hardware-foreseen use case was to mirror traffic for
debugging purposes and to tag it with a special VLAN for this purpose),
but we can force the original frames to be dropped by removing the
pre-retagging VLAN from the port membership list of the egress port.

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>