ANDROID: lowmemorykiller: account for unevictable pages

lowmemorykiller was not taking into account unevictable pages when
deciding what level to kill. If significant amounts of memory were
pinned, this caused lowmemorykiller to effectively stop at a much higher
level than it should.

bug 31255977

Change-Id: If68b4bc31ed5364fd6e8cae9bec0659f6b114903
Signed-off-by: Tim Murray <timmurray@google.com>
Git-Commit: 15a97d3c46c78589db87083fb07d7262df99b1dc
Git-Repo: https://android.googlesource.com/kernel/common


Signed-off-by: Patrick Daly <pdaly@codeaurora.org>