net: ethernet: lpc_eth: remove CONFIG_OF guard from the driver

The MAC controller device is available on NXP LPC32xx platform only,
and the LPC32xx platform supports OF builds only, so additional
checks in the device driver are not needed.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>