kernel: set foreground/background cpuset from oom_adj/oom_score_adj

This option will move processes automatically to foreground and
background cpuset based on oom_adj/oom_score_adj changes.
The main goals are the same as 'ENABLE_CPUSETS := true' on Android,
reducing background overhead and overall power consumption.
Especially useful if the system is big.LITTLE.
This option requires the userspace to properly setup
/dev/cpuset/foreground and /dev/cpuset/background.
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>

Used:
 https://bitbucket.org/arter97/android_kernel_samsung_exynos7420/commits/9731ebaab64a64134bd498e2e8518141318bfb74
 https://bitbucket.org/arter97/android_kernel_samsung_exynos7420/commits/f9f0f7b2c344e5acccd931cc1f89f1d4b20956b4