net: ethernet: mediatek: fix API usage with skb_free_frag

use skb_free_frag() instead of legacy put_page()

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Acked-by: John Crispin <john@phrozen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>