dt-bindings: power: rpmpd: Add SM8450 to rpmpd binding

Add compatible and constants for the power domains exposed by the RPMH
in the Qualcomm SM8450 platform.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211201072745.3969077-6-vkoul@kernel.org