MIPS: BMIPS: add a smp ops registration helper

Add a helper similar to the generic register_XXX_smp_ops() for bmips.
Register SMP UP ops in case of BMIPS32/3300.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6248/