ARM: Samsung: Define common audio-dma device

The ASoC uses common DMA driver for Audio devices. So it makes
sense to a common audio-dma device shared across all platforms.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>