mlphy(4)/tlphy(4): Remove obsolete drivers

These drivers should have been removed along with tl(4) as part of
7c897ca91fe1cdb785531d2f5aa0d441c1d73142 and r347918 respectively
as these fromer made sure to only ever attach to the latter, e. g.:
<...>
static int
tlphy_probe(device_t dev)
{

if (!mii_dev_mac_match(dev, "tl"))

		return (ENXIO);

<...>