* Add arc_emac to DeviceTree DT description
  "Documentation/devicetree/bindings/net/arc_emac.txt".

* Update defconfig correspondingly

[vgupta: tweaked changelog]
Signed-off-by: NAlexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

N.B. This is old style of hardcoding platform device specific info
in code and it's instantiation thererof using platform_add_devices().
Subsequent patches replace this with DeviceTree based runtime probe.

This patch has been retained just as an example of "don't-do-this" for
newer kernel ports.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>