ath79: WNR612v2: improve device support

ath79: WNR612v2: improve device support

This patch improves ath79 support for Netgear WNR612v2.
Router functionality becomes identical to ar71xx version.

Changes include:
* software control over LAN LEDs via sysfs
* correct MAC addresses for network interfaces
* correct image size in device definition
* dts: 'keys' renamed to 'ath9k-keys'
* dts: 'label-mac-device' set to eth1 (LAN)
* dts: formatting adjustments

Signed-off-by: Michal Cieslakiewicz <michal.cieslakiewicz@wp.pl>
(cherry picked from commit d74324e407de7fb641310070762923f7e4cd2d6c)
[remove label-mac-device]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>