dt-bindings: arm: add Cortex-A78 binding

Add compatible for Cortex-A78 PMU

Signed-off-by: Seiya Wang <seiya.wang@mediatek.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210203055348.4935-3-seiya.wang@mediatek.com


Signed-off-by: Will Deacon <will@kernel.org>