ASoC: fsi: use PIO handler if DMA handler was invalid

PIO handler is not good performance, but works on all platform.
So, switch to PIO handler if DMA handler was invalid case.

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