NET: add ENC28J60 driver using SPI framework

V3: further refinements:
- use priv member instead of container method
- allow setting of MAC address by write_hwaddr method
- avoid shutting down link between commands

Signed-off-by: Reinhard Meyer <u-boot@emk-elektronik.de>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/include/netdev.h b/include/netdev.h
index 71fe805..64e5816 100644
--- a/include/netdev.h
+++ b/include/netdev.h
@@ -54,6 +54,8 @@
 int dnet_eth_initialize(int id, void *regs, unsigned int phy_addr);
 int e1000_initialize(bd_t *bis);
 int eepro100_initialize(bd_t *bis);
+int enc28j60_initialize(unsigned int bus, unsigned int cs,
+	unsigned int max_hz, unsigned int mode);
 int ep93xx_eth_initialize(u8 dev_num, int base_addr);
 int ethoc_initialize(u8 dev_num, int base_addr);
 int eth_3com_initialize (bd_t * bis);