Bug fix: Remove the unused sanitize_zone_movable_limit() definition.

Bug fix: Remove the unused sanitize_zone_movable_limit() definition.

When CONFIG_HAVE_MEMBLOCK_NODE_MAP is not defined, sanitize_zone_movable_limit()
is also not used. So remove it.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Liu Jiang <jiang.liu@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Wu Jianguo <wujianguo@huawei.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Lin Feng <linfeng@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>