ARM: dts: uniphier: remove skeleton.dtsi inclusion

Linux Commit 9c0da3cc61f1 ("ARM: dts: explicitly mark skeleton.dtsi
as deprecated") declared that skeleton.dtsi was deprecated.

Move the memory node below to suppress warnings of FDTGREP.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>