BACKPORT: drm/virtio: Drop deprecated load/unload initialization

Move the code around so the driver is probed the bus
.probe and removed from the bus .remove callbacks.
This commit is just a cleanup and shouldn't affect
functionality.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20190108145930.15080-1-ezequiel@collabora.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit d516e75c71c9853ef70a9c476d11a97b69380147)
Bug: 153580313
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: I3ad8b26ab1a9c7dc6e0a5686845ccb9dc37c49da