b53: Allow using all ports on BCM53012

This chipset has at least 8 usable ports, e.g. Netgear R8000 has ports
5, 7 and 8 connected to Ethernet interfaces:
vlan1ports=0 1 2 3 5 7 8*
vlan2ports=4 8u
Port 6 seems to be always disabled.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45676 3c298f89-4303-0410-b956-a3cf2f4a3e73