Rename sz_damon_region() to damon_sz_region(), and move it to
"include/linux/damon.h", because in many places, we can to use this func.

Link: https://lkml.kernel.org/r/20220927001946.85375-1-xhao@linux.alibaba.comSigned-off-by: NXin Hao <xhao@linux.alibaba.com>
Suggested-by: NSeongJae Park <sj@kernel.org>
Reviewed-by: NSeongJae Park <sj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>