[MIPS] Add topology_init.

A recent patch introduced cpu topology in sysfs.  When you run a kernel
with SMP and sysfs enabled, you now get an Oops on boot. The following
patch fixes that by adding topology_init to arch/mips/kernel/smp.c. The
code is copied from arch/s390/kernel/smp.c.

Signed-off-by: Rojhalat Ibrahim <imr@rtschenk.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>