fs/dyn_sync_cntrl: dynamic sync control; enabled KSM

The dynamic sync control interface uses Android kernel's unique early
suspend / lat resume interface.

While screen is on, file sync is disabled
when screen is off, a file sync is called to flush all outstanding writes
and restore file sync operation as normal

Change-Id: If305bf9014d0c164c5a1becc4006a51a0512853f