mm, docs: fix comments that mention mem_hotplug_end()

Comments that mention mem_hotplug_end() are confusing as there is no
function called mem_hotplug_end().  Fix them by replacing all the
occurences of mem_hotplug_end() in the comments with mem_hotplug_done().

[[email protected]: grammatical fixes]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yun-Ze Li <[email protected]>
Cc: Souptick Joarder <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
3 files changed