dt-bindings: vendor-prefixes: favor "gateworks" over "gw"

There are two vendor prefixes for Gateworks: "gw" and "gateworks".
Favor the longer one (more descriptive) and mark "gw" as deprecated so
it will not be used in new bindings.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201003103335.23404-1-krzk@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>