block: Add Zen I/O scheduler

Similar to SIO, primarily based on no-op and deadline. Intended to be mostly FCFS. Simpler than SIO in many ways, one of them being write requests/read requests have mostly the same priority.

Conflicts:

	block/Makefile
Edit ROW
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.

Signed-off-by: Paul Reioux <reioux@gmail.com>