drm/radeon: introduce gem_to_radeon_bo helper

... and switch it to container_of upcasting.

v2: converted new pageflip code-paths.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_cs.c b/drivers/gpu/drm/radeon/radeon_cs.c
index 35b5eb8..8c19169 100644
--- a/drivers/gpu/drm/radeon/radeon_cs.c
+++ b/drivers/gpu/drm/radeon/radeon_cs.c
@@ -75,7 +75,7 @@
 				return -ENOENT;
 			}
 			p->relocs_ptr[i] = &p->relocs[i];
-			p->relocs[i].robj = p->relocs[i].gobj->driver_private;
+			p->relocs[i].robj = gem_to_radeon_bo(p->relocs[i].gobj);
 			p->relocs[i].lobj.bo = p->relocs[i].robj;
 			p->relocs[i].lobj.wdomain = r->write_domain;
 			p->relocs[i].lobj.rdomain = r->read_domains;