bhyve: add helper func to add acpi resources

These helper function can be used to assign acpi resources to an
acpi_device.

Reviewed by: markj
MFC after: 1 week
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D38328

(cherry picked from commit 13a1df5b85e992570f45248bfe9d581dc182b755)