Move the RK3399 specifics to a SoC specific init function to make
the way free for supporting other SoCs later.

Link: https://lore.kernel.org/lkml/20230704093242.583575-5-s.hauer@pengutronix.de/Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>