ASoC: fsi: SPDIF format become independent from platform flags

Current FSI driver is using platform information pointer,
but it is not good design for DT support.
This patch makes spdif format
independent from platform information pointer.

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