ASoC: fsi: merge fsi_data_push/pop to fsi_fifo_data_ctrl

Current FSI driver had data push/pop functions.
But the main operation of these 2 were very similar.
This mean it is possible to merge these to 1 function.

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>