dt-bindings: vendor-prefixes: Add ys vendor prefix

Add prefix for Shenzhen Yashi Changhua Intelligent Technology Co., Ltd.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/efa9b6da947e0cd87ec47c1a211690045304989b.1605688147.git.agx@sigxcpu.org