drm/virtio: Use dev_is_pci()

Use common dev_is_pci() helper to replace the strcmp("pci") used by driver.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220630200726.1884320-9-dmitry.osipenko@collabora.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>