board: add support for the i.MX6 Wandboard platform

Wandboard is a low cost iMX6 system consiting of an EDM standard
processor module and a small base board.

http://www.wandboard.org



Signed-off-by: Stephan Hoffmann <sho@relinux.de>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>