dt-bindings: add vendor-prefix for neonode

Neonode Inc. is the Manufacturer of the zforce infraread touchscreens
used in a lot of ebook readers and supported by the zforce_ts driver.

Signed-off-by: Heiko Stuebner <heiko.stuebner@bqreaders.com>
Signed-off-by: Rob Herring <robh@kernel.org>