bhyve: trap protected BAR regions of passthru devices

At the moment, the list of protected BAR regions is unused by the passthru
emulation. Make use of it when mapping the BAR regions. This causes bhyve to
trap those regions.

Reviewed by: jhb
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D45340