net: ll_temac: Fix and simplify error handling by using devres functions

As a side effect, a few error cases are fixed.

If of_iomap() of sdma_regs failed, no error code was returned.  Fixed to
return -ENOMEM similar to of_iomap() fail of regs.

If sysfs_create_group() or register_netdev() failed, lp->phy_node was not
released.

Finally, the order in remove function is corrected to be reverse order
of what is done in probe, i.e. calling temac_mdio_teardown() last, so we
unregister the netdev that most likely is using the mdio_bus first.

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