ASoC: fsi: tidyup: move fsi_fifo_init() onto fsi_hw_startup()

fsi_fifo_init() is called only from fsi_hw_startup()

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