phy: Fix phy_device_free memory leak

Fix memory leak in phy_device_free() for the case when phy_device*
returned by phy_device_create() is not registered in the system.

Bug description:
phy_device_create() sets name of kobject using dev_set_name(), which
allocates memory using kvasprintf(), but this memory isn't freed if
the underlying device isn't registered properly, because kobject_cleanup()
is not called in that case. This can happen (and actually is happening on
our machines) if phy_device_register(), called by mdiobus_scan(), fails.

Patch description:
Embedded struct device is initialized in phy_device_create() and it
counterpart phy_device_free() just drops one reference to the device,
which leads to proper deinitialization including releasing the kobject
name memory.

Signed-off-by: Petr Malat <oss@malat.biz>
Signed-off-by: David S. Miller <davem@davemloft.net>