net: ethernet: ti: cpsw: fix device and of_node leaks

Make sure to drop the references taken by of_get_child_by_name() and
bus_find_device() before returning from cpsw_phy_sel().

Note that holding a reference to the cpsw-phy-sel device does not
prevent the devres-managed private data from going away.

Fixes: 5892cd13

 ("drivers: net: cpsw-phy-sel: Add new driver...")
Cc: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>