of: Add Boundary Devices Inc. vendor prefix

This patch adds the vendor prefix for Boundary Devices Inc. which is a
supplier of ARM-based single board computers and System-on-Modules for
the general embedded market.

Website: http://boundarydevices.com/

Signed-off-by: Gary Bisson <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

Documentation/devicetree/bindings/vendor-prefixes.txt

···
 avic	Shanghai AVIC Optoelectronics Co., Ltd.
 axis	Axis Communications AB
 bosch	Bosch Sensortec GmbH
+boundary	Boundary Devices Inc.
 brcm	Broadcom Corporation
 buffalo	Buffalo, Inc.
 calxeda	Calxeda