ramips: switch ucidef_add_switch_vlan() to ucidef_add_switch_ports()

This migrates the final board.d user of ucidef_add_switch_vlan() to the new
ucidef_add_switch_ports() approach, fixing some logic errors for a few boards
along the way.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

SVN-Revision: 47717