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>
diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
index f19682a..9a32d9d 100644
--- a/drivers/gpu/drm/ast/ast_drv.c
+++ b/drivers/gpu/drm/ast/ast_drv.c
@@ -199,6 +199,7 @@
 
 	.load = ast_driver_load,
 	.unload = ast_driver_unload,
+	.set_busid = drm_pci_set_busid,
 
 	.fops = &ast_fops,
 	.name = DRIVER_NAME,