ARM: dts: rockchip: move rk3036 i2s sound-dail-cells into soc dtsi

The Rockchip i2s controller always only has one output connection
hence #sound-dai-cells is always 0. Therefore define it in the soc
dtsi itself instead of in individual boards.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>