net: dsa: b53: Always use dev->vlan_enabled in b53_configure_vlan()

b53_configure_vlan() is called by the bcm_sf2 driver upon setup and
indirectly through resume as well. During the initial setup, we are
guaranteed that dev->vlan_enabled is false, so there is no change in
behavior, however during suspend, we may have enabled VLANs before, so we
do want to restore that setting.

Fixes: dad8d7c6 ("net: dsa: b53: Properly account for VLAN filtering")
Fixes: 967dd82f ("net: dsa: b53: Add support for Broadcom RoboSwitch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>