percpu: use the right flag for get_vm_area()

get_vm_area() only accepts VM_* flags, not GFP_*.

And according to the doc of get_vm_area(), here should be
VM_ALLOC.
Signed-off-by: WANG Cong <amwang@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>

mm/percpu.c

@@ -749,7 +749,7 @@ static struct pcpu_chunk *alloc_pcpu_chunk(void)
 	chunk->map[chunk->map_used++] = pcpu_unit_size;
 	chunk->page = chunk->page_ar;
 
-	chunk->vm = get_vm_area(pcpu_chunk_size, GFP_KERNEL);
+	chunk->vm = get_vm_area(pcpu_chunk_size, VM_ALLOC);
 	if (!chunk->vm) {
 		free_pcpu_chunk(chunk);
 		return NULL;