Moved initialization of Blackfin EMAC Ethernet controller to board_eth_init()

Added board_eth_init() function to bf537-stamp board.
Removed initialization for the Blackin EMAC driver from net/eth.c

Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/drivers/net/bfin_mac.c b/drivers/net/bfin_mac.c
index fe56949..3ee5d96 100644
--- a/drivers/net/bfin_mac.c
+++ b/drivers/net/bfin_mac.c
@@ -88,7 +88,7 @@
 
 	eth_register(dev);
 
-	return 1;
+	return 0;
 }
 
 static int bfin_EMAC_send(struct eth_device *dev, volatile void *packet,