net: dsa: install VLANs into the master's RX filter too

Most DSA switch tags shift the EtherType to the right, causing the
master to not parse the VLAN as VLAN.
However, not all switches do that (example: tail tags, tag_8021q etc),
and if the DSA master has "rx-vlan-filter: on" in ethtool -k, then we
have a problem.

Therefore, we could populate the VLAN table of the master, just in case
(for some switches it will not make a difference), so that network I/O
can work even with a VLAN filtering master.

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>