soc: renesas: rcar-sysc: Enable Clock Domain for I/O devices

soc: renesas: rcar-sysc: Enable Clock Domain for I/O devices

On R-Car H3, some power areas (e.g. A3VP) contain I/O devices, which are
also part of the CPG/MSSR Clock Domain.
On all R-Car SoCs, devices in the "always-on" PM Domain are part of the
Clock Domain served by the CPG/MSSR or CPG/MSTP driver.

Hook up the CPG/MSTP or CPG/MSSR Clock Domain attach/detach callbacks to
enable power management using module clocks. Which callback to hook up
depends on the presence of device nodes compatible with
"renesas,cpg-mstp-clocks". This clears the path for a future migration
from the CPG/MSTP to the CPG/MSSR driver on R-Car H1 and
Gen2.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>