drm/panel: st7703: Add Powkiddy RGB30 Panel Support

The Powkiddy RGB30 4 inch panel is a 4 inch 720x720 DSI panel used in
the Powkiddy RGB30 handheld gaming device. Add support for it.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231013183918.225666-4-macroalpha82@gmail.com