arm64: dts: renesas: white-hawk-cpu: Factor out common parts

Factor out the parts on the White Hawk CPU board that are also present
on the White Hawk Single board, so they can be reused when introducing
support for the latter.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/50676e7e9ac1c50ab450c030481f60ece4c3947e.1706192990.git.geert+renesas@glider.be