aries-common: zRAM: only read one page at a time

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

Change-Id: I127b56fdd8f160ba378778320dc711520d9b82e2
aries-common: enable KSM by default

Was enabled by default by Google for crespo

Change-Id: I0951eeed152020e684e9e9e7aa17bac05120d044