ARM: dts: exynos5250: move common i2s properties to exynos5 dtsi

I2S nodes shares some properties across exynos5 SoCs (exynos5250
and exyno5420). Common code is moved to exynos5.dtsi which is
included in exyno5250 and exynos5420 SoC files.

Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>