PM / devfreq: rockchip-dfi: add support for RK3588

Add support for the RK3588 to the driver. The RK3588 has four DDR
channels with a register stride of 0x4000 between the channel
registers, also it has a DDRMON_CTRL register per channel.

Link: https://lore.kernel.org/all/20231018061714.3553817-20-s.hauer@pengutronix.de/
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>