dt-bindings: vendor-prefixes: Add Xingbangda

Shenzhen Xingbangda Display Technology Co., Ltd is a company which
produces LCD modules. It supplies the LCD panels for the PinePhone.

Add the vendor prefix of it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Ondrej Jirman <megous@megous.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200701162928.1638874-2-megous@megous.com