clk: renesas: cpg-mssr: Set GENPD_FLAG_ALWAYS_ON for clock domain

The CPG/MSSR Clock Domain driver does not implement the
generic_pm_domain.power_{on,off}() callbacks, as the domain itself
cannot be powered down.  Hence the domain should be marked as always-on
by setting the GENPD_FLAG_ALWAYS_ON flag, to prevent the core PM Domain
code from considering it for power-off, and doing unnessary processing.

Note that this only affects RZ/A2 SoCs.  On R-Car Gen2 and Gen3 SoCs,
the R-Car SYSC driver handles Clock Domain creation, and offloads only
device attachment/detachment to the CPG/MSSR driver.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/clk/renesas/renesas-cpg-mssr.c

@@ -551,7 +551,8 @@ static int __init cpg_mssr_add_clk_domain(struct device *dev,
 
 	genpd = &pd->genpd;
 	genpd->name = np->name;
-	genpd->flags = GENPD_FLAG_PM_CLK | GENPD_FLAG_ACTIVE_WAKEUP;
+	genpd->flags = GENPD_FLAG_PM_CLK | GENPD_FLAG_ALWAYS_ON |
+		       GENPD_FLAG_ACTIVE_WAKEUP;
 	genpd->attach_dev = cpg_mssr_attach_dev;
 	genpd->detach_dev = cpg_mssr_detach_dev;
 	pm_genpd_init(genpd, &pm_domain_always_on_gov, false);