drm: Add checks for atomic_[duplicate/destroy]_state with atomic drivers

This patch add checks for atomic_[duplicate/destroy]_state of
drm_[connector/crtc/plane]_funcs for atomic drivers in the relevant
drm_*_init functions since these callback are mandatory for atomic drivers.

Update the kerneldoc comments for those callbacks.

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180525012555.GA8448@haneen-vb
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 002b244..549b8950 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -195,6 +195,10 @@
 	struct ida *connector_ida =
 		&drm_connector_enum_list[connector_type].ida;
 
+	WARN_ON(drm_drv_uses_atomic_modeset(dev) &&
+		(!funcs->atomic_destroy_state ||
+		 !funcs->atomic_duplicate_state));
+
 	ret = __drm_mode_object_add(dev, &connector->base,
 				    DRM_MODE_OBJECT_CONNECTOR,
 				    false, drm_connector_free);