Restore DTS node of PCIe controller for A38X boards

[mw_semihalf.com]

Summary

Add pcie-controller node as a bus-parent of pcie nodes for Armada38x
boards. This reduces diff between Linux and FreeBSD PCIe device tree
representation to the minimum. This commit also allows for using multiple
PCIe ports, thanks to the recent driver updates, which support such
hierarchy. Restore original PCIe nodes in armada-385.dtsi and
apply necessary changes in hitherto unused armada-380.dtsi.