phy: lynx-28g: cancel the CDR check work item on the remove path

The blamed commit added the CDR check work item but didn't cancel it on
the remove path. Fix this by adding a remove function which takes care
of it.

Fixes: 8f73b37c

 ("phy: add support for the Layerscape SerDes 28G")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>