mm/damon: remove duplicate get_monitoring_region() definitions

mainline inclusion
from mainline-v6.2-rc6
commit 0d83b2d8
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6MRUG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0d83b2d89dbfad17b62d4e7fb8f0b0525ba1a204

--------------------------------

In lru_sort.c and reclaim.c, they are all defining get_monitoring_region()
function, there is no need to define it separately.

As 'get_monitoring_region()' is not a 'static' function anymore, we try to
use a prefix to distinguish with other functions, so there rename it to
'damon_find_biggest_system_ram'.

Link: https://lkml.kernel.org/r/20220909213606.136221-1-sj@kernel.org


Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ze Zuo <zuoze1@huawei.com>