PM: hibernate: Don't mark comment as kernel-doc

Change the comment to a normal (non-kernel-doc) comment to avoid
these kernel-doc warnings:

kernel/power/snapshot.c:335: warning: This comment starts with '/**', but
 isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * Data types related to memory bitmaps.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>