Asynchronous Fsync: initial extraction of Async Fsync from HTC

Signed-off-by: Paul Reioux <reioux@gmail.com>
Signed-off-by: Dan Trifan <jimsth@gmail.com>
defconfig: disable DYNAMIC_FSYNC and enable ASYNC_FSYNC

Signed-off-by: Dan Trifan <jimsth@gmail.com>