ARM: S5P6442: Enable I2S device to work on SMDK6442

Add missing virtual ASoC DMA device.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
[kgene.kim@samsung.com: minor changed title]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>