net: ll_temac: Extend support to non-device-tree platforms

Support initialization with platdata, so the driver can be used on
non-device-tree platforms.

For currently supported device-tree platforms, the driver should behave
as before.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>