ARM: dts: exynos: Cleanup Odroid-X2 and enable sound on Odroid-X

Odroid-X2 differs from Odroid-X only in RAM and prime CPU.
Remove doubled nodes from exynos4412-odroidx2.dts and move
sound node to exynos4412-odroidx.dts to enable sound on both boards.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>