feat(fvp): fdts: update rtsm_ve DT files from the Linux kernel

feat(fvp): fdts: update rtsm_ve DT files from the Linux kernel

The existing DT files for the base FVP model are having some issues,
that lead to warnings reported by the device tree compiler.

Those (and many other issues around (updated) DT binding compliance)
were fixed in the Linux kernel tree, so let's sync those files back into
TF-A.
We cannot copy the files "as is" for now, since we rely on certain custom
properties to be added (max-pwr-lvl in the PSCI node, SDEI nodes, etc).

Merge in the changed parts of the Linux kernel DT (from Linux v6.0-rc1),
and rework the base file to allow including the motherboard.dtsi
unchanged. This should make any future update less painful.

As this also affects the FVP VE boards (Cortex-A7 and Cortex-A5), since
they share the motherboard include file, fix them up as well.

Change-Id: I4f74d05e5583747f8849e32f246f74aeec7a9c60
Signed-off-by: Andre Przywara <andre.przywara@arm.com>