ARM: dts: s3c24xx: Remove skeleton.dtsi and fix DTC warning for /memory

Remove the usage of skeleton.dtsi to fix the DTC warning:

    arch/arm/boot/dts/s3c2416-smdk2416.dtb: Warning (unit_address_vs_reg):
        /memory: node has a reg or ranges property, but no unit name

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>