phylib: Add autoload support for the LXT973 phy.

Commit e13647c1 (phylib: Add support for the LXT973 phy.) added a new ID
but neglected to also add it to the MODULE_DEVICE_TABLE.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>