ASoC: fsi: bugfix: ensure dma is terminated

FSI DMAEngine has to be stopped certainly at the start/stop time.
Without this patch, it will include noise on playback.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>