bcm63xx: switch to b53 and swconfig

Switch to using the B53 switch driver where appropriate.

Use a non-tagged default config where it isn't confirmed to be
working.

Remove the switch configuration in preinit as the switch will now
be configured by the driver  to use port isolation to prevent leakage
between lan and wan.

While at it, also provide a switch config for Neufbox 6.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35307 3c298f89-4303-0410-b956-a3cf2f4a3e73