net: dsa: sja1105: stop using priv->vlan_aware

Now that the sja1105 driver is finally sane enough again to stop having
a ternary VLAN awareness state, we can remove priv->vlan_aware and query
DSA for the ds->vlan_filtering value (for SJA1105, VLAN filtering is a
global property).

Also drop the paranoid checking that DSA calls ->port_vlan_filtering
multiple times without the VLAN awareness state changing. It doesn't,
the same check is present inside dsa_port_vlan_filtering too.

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>