percpu: don't forget to free the temporary struct pcpu_alloc_info

Unlike the SMP case, the !SMP case does not free the memory for struct
pcpu_alloc_info allocated in setup_per_cpu_areas(). And to give it a
chance of being reused by the page allocator later, align it to a page
boundary just like its size.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Dennis Zhou <dennisszhou@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>