dt-bindings: arm: cpus: Add ARM Cortex-A78

The ARM Cortex-A78 CPU can be found in a number of recent SoCs such as
the NVIDIA Tegra234 (Orin).

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Robin Murphy <robin.muephy@arm.com>
Link: https://lore.kernel.org/r/20211112131904.3683428-1-thierry.reding@gmail.com


Signed-off-by: Rob Herring <robh@kernel.org>