dt-bindings: power: qcom,rpmpd: document qcs615 RPMh power domains

Add compatible string for the RPMh power domains on qcs615 platform.

Signed-off-by: Tingguo Cheng <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/20240927-[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/power/qcom,rpmpd.yaml

···
           - qcom,msm8998-rpmpd
           - qcom,qcm2290-rpmpd
           - qcom,qcs404-rpmpd
+          - qcom,qcs615-rpmhpd
           - qcom,qcs8300-rpmhpd
           - qcom,qdu1000-rpmhpd
           - qcom,qm215-rpmpd