dt-bindings: arm: coresight: Add 'power-domains' property

Coresight components may be in a power domain which is the case for the Arm
Juno board. Allow a single 'power-domains' entry for Coresight components.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20220721212718.1980905-1-robh@kernel.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>