tmf: Change to timer based coalescing of background requests

tmf: Change to timer based coalescing of background requests

Coalescing of foreground requests are still based on signal
synchronization using start and end sync signal. Foreground requests
are meant for short and higher priority requests and need to be
processed right away.

Change-Id: Iae0cf886e4c932b1620a13057a9e1242702e2089
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/20824
Tested-by: Hudson CI
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
IP-Clean: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>