drm: Remove drm_driver->set_busid hook

The only special-case is pci devices, and we can easily handle this in
the core. Do so and drop a pile of boilerplate from drivers.

Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170524145212.27837-5-daniel.vetter@ffwll.ch

drivers/gpu/drm/savage/savage_drv.c

@@ -55,7 +55,6 @@ 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,