soc: qcom: smd-rpm: Add compatible for MSM8909

Add the new "qcom,rpm-msm8909" compatible to the driver so the interface
to the Resource Power Manager (RPM) is initialized correctly on MSM8909.

Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220705143523.3390944-3-stephan.gerhold@kernkonzept.com