drm/rockchip: dsi: add rk3568 support

Add the compatible and GRF definitions for the RK3568 soc.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220906174823.28561-4-macroalpha82@gmail.com