dt-bindings: Add vendor prefix for Hydis technologies

This vendor has produced a number of display panels,
including HVA40WV1.

Cc: devicetree@vger.kernel.org
Cc: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200223121841.26836-1-linus.walleij@linaro.org