ASoC: fsi: update for dmaengine prep_slave_sg fallout.

ASoC: fsi: update for dmaengine prep_slave_sg fallout.

Leading up to the ->device_prep_slave_sg change in
7a8d32cca0c7ca4174d9d26c22fb2ce298318bd3 'dmaengine: add context
parameter to prep_slave_sg and prep_dma_cyclic' a generic wrapper was
added in place to guard against the API change, though the fsi driver
wasn't updated in the process (presumably its dmaengine support hadn't
been merged yet at the time). This trivially switches over to the new
wrapper and gets it building again.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>