pci_host_generic: Add Synopsys Designware PCIe controller quirk

Due to the quirky nature of the Synopsys Designware PCIe IP,
the type 0 configuration is broadcast and whatever device
is plugged into slot, will appear at each 32 device
positions of bus0. Mitigate the issue by filtering out
duplicated devices on this bus for both DT and ACPI cases.

Reviewed by: mw
Sponsored by: Semihalf
MFC: after 3 weeks
Differential revision: https://reviews.freebsd.org/D31887