ARM: S5PC100: Add S/PDIF platform device

This patch add S/PDIF platform device to support S/PDIF PCM audio
on S5PC100.

Signed-off-by: Seungwhan Youn <sw.youn@samsung.com>
Acked-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>