percpu: match chunk allocator declarations with definitions

At some point the function declaration parameters got out of sync with
the function definitions in percpu-vm.c and percpu-km.c. This patch
makes them match again.

Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>