ASoC: rcar: Fix dma direction type

dmaengine_prep_slave_single() expects a enum dma_transfer_direction and not a
enum dma_data_direction. Since the integer representations of both DMA_TO_DEVICE
and DMA_MEM_TO_DEV aswell as DMA_FROM_DEVICE and DMA_DEV_TO_MEM have the same
value the code worked fine even though it was using the wrong type.

Fixes the following warning from sparse:
	sound/soc/sh/rcar/core.c:227:49: warning: mixing different enum types
	sound/soc/sh/rcar/core.c:227:49:     int enum dma_data_direction  versus
	sound/soc/sh/rcar/core.c:227:49:     int enum dma_transfer_direction

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@linaro.org>