Support multi-port PCIe hierarchy in Marvell boards DTS

This commit is another part of preparation for PCIe multi-port
support for Marvell SoCs. Some device trees include pcie-controller
node as a bus-parent of pcie nodes. This patch adds support for
new bus, collects and configures device informations and finally
adds PCIB devices as a childs of pcie-controller in Newbus hierarchy.

Submitted by: Marcin Mazurek <mma@semihalf.com>
Obtained form: Semihalf
Sponsored by: Stormshield
Reviewed by: https://reviews.freebsd.org/D10906