padata: Fix cpu index counting

The counting of the cpu index got lost with a recent commit.
This patch restores it. This fixes a hang of the parallel worker
threads on cpu hotplug.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

kernel/padata.c

@@ -408,6 +408,7 @@ static void padata_init_pqueues(struct parallel_data *pd)
 		pqueue = per_cpu_ptr(pd->pqueue, cpu);
 		pqueue->pd = pd;
 		pqueue->cpu_index = cpu_index;
+		cpu_index++;
 
 		__padata_list_init(&pqueue->reorder);
 		__padata_list_init(&pqueue->parallel);