MIPS: BCM63XX: disable SMP also on BCM3368

BCM3368 has the same shared TLB as BCM6358.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6239/