drm: add driver->set_busid() callback

One step closer to dropping all the drm_bus_* code:
Add a driver->set_busid() callback and make all drivers use the generic
helpers. Nouveau is the only driver that uses two different bus-types with
the same drm_driver. This is totally broken if both buses are available on
the same machine (unlikely, but lets be safe). Therefore, we create two
different drivers for each platform during module_init() and set the
set_busid() callback respectively.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/savage/savage_drv.c

@@ -57,6 +57,7 @@ static struct drm_driver driver = {
 	.preclose = savage_reclaim_buffers,
 	.lastclose = savage_driver_lastclose,
 	.unload = savage_driver_unload,
+	.set_busid = drm_pci_set_busid,
 	.ioctls = savage_ioctls,
 	.dma_ioctl = savage_bci_buffers,
 	.fops = &savage_driver_fops,