mm: decreased swappiness to 20

Change-Id: Ic822eb754a656afe2286f3efda33d11cb0b4df40
Signed-off-by: zwliew <zhaoweiliew@gmail.com>
params: fix potential memory leak in add_sysfs_param()

thanks to David Woodhouse

Change-Id: I88098d181b0aaf58e5708ebd69ccc7a74bff45a7
Signed-off-by: zwliew <zhaoweiliew@gmail.com>