drm/radeon: use variable flags as parameter

To be consistent with amdgpu driver, use "flags" as the parameter because
it is already assigned as "ent->driver_data".

Reviewed-by: Thomas Zimmermann <[e-mail]>
Tested-by: Thomas Zimmermann <[e-mail]>
Signed-off-by: Wu Hoi Pok <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_drv.c

···
 	if (ret)
 		goto err_agp;
 
-	ret = drm_dev_register(ddev, ent->driver_data);
+	ret = drm_dev_register(ddev, flags);
 	if (ret)
 		goto err_agp;