percpu: make pcpu_alloc_chunk() use pcpu_mem_free() instead of kfree()

commit 5a838c3b60e3a36ade764cf7751b8f17d7c9c2da upstream.

pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
	BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long)

It hardly could be ever bigger than PAGE_SIZE even for large-scale machine,
but for consistency with its couterpart pcpu_mem_zalloc(),
use pcpu_mem_free() instead.

Commit b4916cb17c26 ("percpu: make pcpu_free_chunk() use
pcpu_mem_free() instead of kfree()") addressed this problem, but
missed this one.

tj: commit message updated

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 099a19d91ca4 ("percpu: allow limited allocation before slab is online)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>