MIPS: lantiq: register smp_ops on non-smp platforms

Lantiq uses a common kernel config for devices with 24Kc and 34Kc cores.
The changes made previously to add support for interrupts on all cores
work on 24Kc platforms with SMP disabled and 34Kc platforms with SMP
enabled. This patch fixes boot issues on Danube (single core 24Kc) with
SMP enabled.

Fixes: 730320fd

 ("MIPS: lantiq: enable all hardware interrupts on second VPE")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>