[SPARC64]: Clear cpu_{core,sibling}_map[] in smp_fill_in_sib_core_maps()

When we hot-plug in new cpus, the core_id and proc_id of existing
cpus can change.  So in order to set the cpu groups correctly we
need to clear the maps out completely first.

Signed-off-by: David S. Miller <davem@davemloft.net>