dt-bindings: power: rpmpd: Add SM8550 to rpmpd binding

Add compatible and constants for the power domains exposed by the RPMH
in the Qualcomm SM8550 platform.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221116111745.2633074-2-abel.vesa@linaro.org