net: altera_tse: release phylink resources in tse_shutdown()

Call phylink_disconnect_phy() in tse_shutdown() to release the
resources occupied by phylink_of_phy_connect() in the tse_open().

Fixes: fef29982

 ("net: altera: tse: convert to phylink")
Signed-off-by: Liu Jian <liujian56@huawei.com>
Link: https://lore.kernel.org/r/20221123011617.332302-1-liujian56@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>