dt-bindings: vendor-prefixes: Add nutsboard

NutsBoard (http://nutsboard.org/

) is an organization and focus
on ARM based embedded boards with open source software.

Signed-off-by: YuanCheng Cheng <onlywig@gmail.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>