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/qxl/qxl_drv.c

@@ -235,6 +235,8 @@ static struct drm_driver qxl_driver = {
 	.enable_vblank = qxl_noop_enable_vblank,
 	.disable_vblank = qxl_noop_disable_vblank,
 
+	.set_busid = drm_pci_set_busid,
+
 	.dumb_create = qxl_mode_dumb_create,
 	.dumb_map_offset = qxl_mode_dumb_mmap,
 	.dumb_destroy = drm_gem_dumb_destroy,