Change DTS entry of PCIe controller for Armada38x

Invalid (in FreeBSD) definition of PCI controller was
replaced with another one, working in FreeBSD environment.

PCI controller's entry had to move from its parent node
so as to be recognized properly by FBSD.

PCI was enabled in kernel configuration file.

Obtained from: Semihalf
Sponsored by: Stormshield
Submitted by: Bartosz Szczepanek <bsz@semihalf.com>
Differential revision: https://reviews.freebsd.org/D4379