util: remove LIST_ADD macro

Just use the inlined function directly. The macro was replaced with
the function in ebe304fa54.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>

src/mesa/state_tracker/st_manager.c

@@ -1036,7 +1036,7 @@ st_framebuffer_reuse_or_create(struct st_context *st,
          }
 
          /* add to the context's winsys buffers list */
-         LIST_ADD(&cur->head, &st->winsys_buffers);
+         list_add(&cur->head, &st->winsys_buffers);
 
          st_framebuffer_reference(&stfb, cur);
       }