drop_caches: drop pagecaches on screen-off

This will ensure enough free memory on screen-on request

Change-Id: I545849fbbad67564952d9f3d6605b556bb53bb66
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>

drop_caches: drop caches after 200ms

This avoids potential slowdowns in screen-off or suspend routine.

Change-Id: I59b36755fba14c1392546e4485324233ec6603f0

drop_caches: rename "now" to "suspend"

Change-Id: Ia04c3e39fd55b27a3bc959a5316f9439d71b12a2
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>

drop_caches: drop slab objects as well

Change-Id: I7614123fd948bce91d52411cfd0a82f70e761d96
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: minaripenguin <minaripenguin@users.noreply.github.com>