init: add pages_to_scan and sleep_millisecs KSM tunables

Based on: https://source.android.com/devices/low-ram.html

Change-Id: I5410edc3134233bf4486e676adc508581d033c40
Merge branch 'cm-11.0' of https://github.com/Mustaavalkosta/android_device_htc_ace into cd-4.4