From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
__offline_isolated_pages() and test_pages_isolated() are used by memory
hotplug. These functions require that range is in a single zone but
there is no code about it because memory hotplug checks it before calling
these functions. Not to confuse future user of these functions,
this patch adds comment on them.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>