fs/dyn_sync_cntrl: dynamic sync control

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.
Conflicts:
	fs/Kconfig
	fs/sync.c

Backported to 2.6.39.4 by pengus77 <ivan@cerrato.biz>

Change-Id: I42d964151cdbc2dadb378655f9d9ab78543fb042