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.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: José Vázquez <pepvf@mixmail.com>