ip17xx: Initialize VLAN state upon reset

Let VLAN state variables be initialized not only when the enable VLAN bit
is toggled, but also upon reset.

At this point, this should be a no-op, since the driver reads the current
hardware state before doing any modifications anyway, but I plan to keep
some state locally in the subsequent patches.

Signed-off-by: Martin Mares <mj@ucw.cz>
Signed-off-by: Patrick Horn <patrick.horn@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@21716 3c298f89-4303-0410-b956-a3cf2f4a3e73