ASoC: fsi: simultaneous playback/recorde support

Current FSI driver had not cared about simultaneous
playback/capture on same port.
This patch add new fsi_stream struct to care it,
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>