When you have a static network environment but more than one network
device on your machine it is necessary to provide the <device> parameter
to the ip parameter at kernel cmd line.

The device name assigned by Linux cannot in general be predicted as it
depends on driver bind order.

This patch introduces a new property linux.devname to eth devices.
The value is added to bootargs per interface and can be changed in
env/network/INTF

Based on patch by Gavin Schenk <g.schenk@eckelmann.de>.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>