lowmemorykiller: Introduce sysfs node for ALMK and PPR adj threshold

The grouping of tasks based on oom_score_adj values change from
one framework to another. This requires corresponding changes in
the threshold values set for almk and per process reclaim.
Introduce sysfs nodes to set threshold adj for process reclaim
and adaptive LMK dynamically.

Change-Id: Ib7565bfd5d2e93aa4ff8fdd20414cac0a0f38bf7
Signed-off-by: Suyog Sarda <ssarda@codeaurora.org>
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>