dt-bindings: clock: qcom,rpmcc: Add MSM8909

Document the "qcom,rpmcc-msm8909" compatible for the clocks available
via the RPM on the MSM8909 SoC.

Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220706134132.3623415-6-stephan.gerhold@kernkonzept.com