soc: qcom: rpmpd: Add compatible for MSM8909

MSM8909 has the same power domains as MSM8916, so just define another
compatible for the existing definition.

Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220705143523.3390944-5-stephan.gerhold@kernkonzept.com