drm/atomic: Avoid unused-but-set-variable warning on for_each_old_pla…

…ne_in_state

Artificially use 'plane' and 'old_plane_state' to avoid 'not used' warning.
The precedent has already been set by other macros in the same file.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Liu Ying <victor.liu@nxp.com>

include/drm/drm_atomic.h

@@ -947,7 +947,10 @@ void drm_state_dump(struct drm_device *dev, struct drm_printer *p);
 	     (__i)++)							\
 		for_each_if ((__state)->planes[__i].ptr &&		\
 			     ((plane) = (__state)->planes[__i].ptr,	\
-			      (old_plane_state) = (__state)->planes[__i].old_state, 1))
+			      (void)(plane) /* Only to avoid unused-but-set-variable warning */, \
+			      (old_plane_state) = (__state)->planes[__i].old_state, \
+			      (void)(old_plane_state) /* Only to avoid unused-but-set-variable warning */, 1))
+
 /**
  * for_each_new_plane_in_state - iterate over all planes in an atomic update
  * @__state: &struct drm_atomic_state pointer