lowmemorykiller: fix GCC-4.7 compiler warning

Signed-off-by: Paul Reioux <reioux@gmail.com>
LMK: Optimize lowmem_shrink.

By comparing with selected_oom_score_adj instead of min_score_adj,
we may do less calculation.

Signed-off-by: Leon Ma <xindong.ma@intel.com>

Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:
	drivers/staging/android/lowmemorykiller.c
Revert "f2fs: data: AIO optimization compatibility fixup"

This reverts commit 7d77d75b7acb44d0e3cefd7adeb28035be8972c0.
android/lowmemorykiller: fix build while cherry-picking