arm64: dtb: qcom: qrb5165-rb5: add power domain to pcie0 phy

If QCA6391 chip (connected to PCIe0) is not powered at the PCIe probe
time, PCIe0 bus probe will timeout and the device will not be detected.
To ease device power up support, use qca639x as pcie0 phy power-domain.
This allows us to make sure that QCA6391 chip is powered on before PCIe0
probe happens.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>