dt-bindings: add vendor Vertexcom

Add vendor prefix for Vertexcom Technologies, Inc [1].

[1] - http://www.vertexcom.com/



Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>