ENC28J60 is a stand-alone Ethernet controller with SPI Interface
and integrated 10BASE-T PHY.

This driver was ported from linux-3.15.

The most notable barebox driver version changes:
  * add device tree support;
  * drop netif_msg_*() debug level checking;
  * use IF_ENABLED for checking CONFIG_ENC28J60_WRITEVERIFY;
  * add mii_bus support.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>