ARM: dts: add clock provider information for i2s controllers in Exynos5250

Add clock lookup information for i2s controllers on exynos5250 SoC.

Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>