ASoC: fsi: bugfix: correct dma area

FSI driver is using dma_sync_single_xxx(),
but the dma area was not correct.
This patch fix it up.

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