ARM: dts: Add I2S dt node for exynos3250

This patch add I2S (Inter-IC Sound) dt node which supports 1-port
stereo (1 channels) IIS-bus for audio interface with DMA-based
operation.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Inha Song <ideal.song@samsung.com>
Tested-by: Inha Song <ideal.song@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>