dt-bindings: panel-simple-dsi: add Khadas TS050 panel bindings

This add the bindings for the Khadas TS050 1080x1920 5" LCD DSI panel designed to work
with the Khadas Edge-V, Captain, VIM3 and VIM3L Single Board Computers.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204081949.38418-2-narmstrong@baylibre.com