powerpc/numa: use cached value of update->cpu in update_cpu_topology

There isn't any need to keep referring to update->cpu, as we've already
checked cpu == update->cpu at this point.
Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/numa.c

@@ -1512,8 +1512,8 @@ static int update_cpu_topology(void *data)
 		if (cpu != update->cpu)
 			continue;
 
-		unmap_cpu_from_node(update->cpu);
-		map_cpu_to_node(update->cpu, update->new_nid);
+		unmap_cpu_from_node(cpu);
+		map_cpu_to_node(cpu, update->new_nid);
 		vdso_getcpu_init();
 	}