PM / devfreq: rockchip-dfi: Handle LPDDR4X

PM / devfreq: rockchip-dfi: Handle LPDDR4X

In the DFI driver LPDDR4X can be handled in the same way as LPDDR4. Add
the missing case.

Link: https://lore.kernel.org/all/20231018061714.3553817-13-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>