ecore_drm2: Don't clear plane fb on release

We'll need this later for post-page flip bookkeeping, and nothing will
notice that it's not cleared now anyway.

src/lib/ecore_drm2/ecore_drm2_plane.c

@@ -137,7 +137,6 @@ ecore_drm2_plane_release(Ecore_Drm2_Plane *plane)
      eina_list_append(plane->output->fbs, plane->state->fb);
 
    plane->dead = EINA_TRUE;
-   plane->state->fb = NULL;
    plane->state->in_use = EINA_FALSE;
    _fb_atomic_flip_test(plane->output);
 }