PCI: starfive: Enable controller runtime PM before probing host bridge

PCI: starfive: Enable controller runtime PM before probing host bridge

A PCI controller device, e.g., StarFive, is parent to PCI host bridge
device. We must enable runtime PM of the controller before enabling runtime
PM of the host bridge, which will happen in pci_host_probe(), to avoid this
warning:

  pcie-starfive 940000000.pcie: Enabling runtime PM for inactive device with active children

Fix this issue by enabling StarFive controller device's runtime PM before
calling pci_host_probe() in plda_pcie_host_init().

Link: https://lore.kernel.org/r/20241111-runtime_pm-v7-1-9c164eefcd87@quicinc.com
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mayank Rana <quic_mrana@quicinc.com>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>