ARM: dts: uniphier: prepare device trees to use pinctrl in SPL

Add "u-boot,dm-pre-reloc" for device nodes we want in SPL DTB
(spl/u-boot-spl.dtb).

The "soc" node (this is simple-bus node) also needs the property
to bind the pinctrl node located under it.

I am collecting this U-Boot specific hack to the bottom of board
DTS rather than inserting "u-boot,dm-pre-reloc" into SoC DTSI.
My goal is to sync DTSI with Linux for easier maintenance.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>