pci_host_generic:Add pcib_request_feature on ACPI

In the ACPI attachment add support for the pcib_request_feature method.
This uses the common _OSC handling.

Reviewed by: imp, jhb
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D48048

(cherry picked from commit 1f5c50a8617355758510675cb9412f56fed12efc)