ANDROID: mm: oom_kill: reap memory of a task that receives SIGKILL

Free the pages parallely for a task that receives SIGKILL, from ULMK
process, using the oom_reaper. This freeing of pages will help to give
the pages to buddy system well advance.

Add the boot param, reap_mem_when_killed_by=, that configures the
process name, the kill signal to a process from which makes its memory
reaped by oom reaper.

As an example, when reap_mem_when_killed_by=lmkd, then all the processes
that receives the kill signal from lmkd is added to oom reaper.

Not initializing this param makes this feature disabled.

Change-Id: I21adb95de5e380a80d7eb0b87d9b5b553f52e28a
Bug: 171763461
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>