dt-bindings: soc: qcom: smd-rpm: Add MSM8909 to qcom,smd-channels

MSM8909 is using qcom,smd-channels but is missing in the list, add it
there as well.

Fixes: 709d473d ("dt-bindings: soc: qcom: smd-rpm: Add MSM8909")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20230531-rpm-rproc-v3-2-a07dcdefd918@gerhold.netSigned-off-by: Bjorn Andersson <andersson@kernel.org>

Documentation/devicetree/bindings/soc/qcom/qcom,smd-rpm.yaml

@@ -82,6 +82,7 @@ if:
         enum:
           - qcom,rpm-apq8084
           - qcom,rpm-msm8226
+          - qcom,rpm-msm8909
           - qcom,rpm-msm8916
           - qcom,rpm-msm8936
           - qcom,rpm-msm8953