Use rtl8169_set_speed() for link setup in rtl8169_init_one():
- the code which handles the option checking is isolated;
- display (once) a notice message about the deprecated interface;
- rtl8169_open() enables the phy timer if the link is not up;
- rtl8169_set_speed() checks that the netdevice is actually ready
  in order to activate the timer.