dt-bindings: arm: pmu: Document Denver and Carmel PMUs

Add compatible strings for the NVIDIA Denver and Carmel PMUs.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211207150746.444478-1-thierry.reding@gmail.com


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