vbo/dlist: realloc prims array instead of free/malloc
Now that we don't have links to the prim_store->prims pointers, we can replace the free/malloc by a realloc version to grow the prim storage as needed by a list. This will be used in the next commit to avoid splitting lists in multiple vbo_save_vertex_list instances because the prim_store was full. Reviewed-by:Marek Olšák <marek.olsak@amd.com> Part-of: <mesa/mesa!12646>