soc: rockchip: power-domain: add rk3588 mem module support

On RK3588 it's also possible to power down the memory used by the
particular power domains via PMU_MEM_PWR_GATE_SFTCON. This adds
support for this feature.

Tested-by: Vincent Legoll <vincent.legoll@gmail.com>
Co-Developed-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230403193250.108693-3-sebastian.reichel@collabora.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>