pmdomain: renesas: rcar-gen4-sysc: Don't keep unused PM domains powered-on

The recent changes to genpd makes a genpd OF provider that is powered-on at
initialization to stay powered-on, until the ->sync_state() callback is
invoked for it.

This may not happen at all, if we wait for a consumer device to be probed,
leading to wasting energy. There are ways to enforce the ->sync_state()
callback to be invoked, through sysfs or via the probe-defer-timeout, but
none of them in its current form are a good fit for rcar-gen4-sysc PM
domains.

Let's therefore opt-out from this behaviour of genpd for now, by using the
GENPD_FLAG_NO_STAY_ON.

Link: https://lore.kernel.org/all/20250701114733.636510-1-ulf.hansson@linaro.org/
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: 0e789b4 ("pmdomain: core: Leave powered-on genpds on until sync_state")
Fixes: 13a4b7f ("pmdomain: core: Leave powered-on genpds on until late_initcall_sync")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: storulf

drivers/pmdomain/renesas/rcar-gen4-sysc.c

@@ -251,6 +251,7 @@ static int __init rcar_gen4_sysc_pd_setup(struct rcar_gen4_sysc_pd *pd)
 		genpd->detach_dev = cpg_mssr_detach_dev;
 	}
 
+	genpd->flags |= GENPD_FLAG_NO_STAY_ON;
 	genpd->power_off = rcar_gen4_sysc_pd_power_off;
 	genpd->power_on = rcar_gen4_sysc_pd_power_on;