mm: Implement find_get_entries_range_tag()

Implement find_get_entries_range_tag() (actually convert
find_get_entries_tag() tag to it as the only user of
find_get_entries_tag() needs a ranged lookup) and use it in DAX which is
the only user of this interface. This is mostly for consistency with
other page/entry iteration interfaces.

Signed-off-by: Jan Kara <jack@suse.cz>
3 files changed