fs_enet: Fix a memory leak in fs_enet_mdio_probe

There are more memory leaks in the !PPC_CPM_NEW_BINDING case, but that code
will disappear soon along with arch/ppc.

Reported by Daniel Marjamki <danielm77@spray.se> at
http://bugzilla.kernel.org/show_bug.cgi?id=10591

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>