Since commit 9c0da3cc ("ARM: dts: explicitly mark skeleton.dtsi as
deprecated") the inclusion of skeleton.dtsi is deprecated, so
remove it as this file will eventually go away someday.

Move its content to the SoC dtsi file, so that the resultant dtb
is the same.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>