vt/vga: ignore ACPI_FADT_NO_VGA unless running virtualized

There's too many broken hardware out there that wrongly has the
ACPI_FADT_NO_VGA bit set. Ignore it unless running as a virtualized
guest, as then the expectation would be that the hypervisor does
provide correct ACPI tables.

Reviewed by: emaste, 0mp, eugen
Sponsored by: Citrix Systems R&D
PR: 230172

(cherry picked from commit 0518832011caba1e9dcee054d7884797ed8a74c2)