clk: renesas: mstp: Add genpd OF provider at postcore_initcall()

Genpd OF providers must now be registered after genpd bus registration.
However, cpg_mstp_add_clk_domain() is only called from CLK_OF_DECLARE(),
which is too early.  Hence on R-Car M1A, R-Car H1, and RZ/A1, the
CPG/MSTP Clock Domain fails to register, and any devices residing in
that clock domain fail to probe.

Fix this by splitting initialization into two steps:
  - The first part keeps on registering the PM domain with genpd at
    CLK_OF_DECLARE(),
  - The second and new part moves the registration of the genpd OF
    provider to a postcore_initcall().

See also commit c5ae5a0 ("pmdomain: renesas: rcar-sysc: Add
genpd OF provider at postcore_initcall").

Fixes: 18a3a51 ("pmdomain: core: Add the genpd->dev to the genpd provider bus")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/81ef5f8d5d31374b7852b05453c52d2f735062a2.1755073087.git.geert+renesas@glider.be

Author: geertu

drivers/clk/renesas/clk-mstp.c

@@ -303,6 +303,9 @@ void cpg_mstp_detach_dev(struct generic_pm_domain *unused, struct device *dev)
 		pm_clk_destroy(dev);
 }
 
+static struct device_node *cpg_mstp_pd_np __initdata = NULL;
+static struct generic_pm_domain *cpg_mstp_pd_genpd __initdata = NULL;
+
 void __init cpg_mstp_add_clk_domain(struct device_node *np)
 {
 	struct generic_pm_domain *pd;
@@ -324,5 +327,20 @@ void __init cpg_mstp_add_clk_domain(struct device_node *np)
 	pd->detach_dev = cpg_mstp_detach_dev;
 	pm_genpd_init(pd, &pm_domain_always_on_gov, false);
 
-	of_genpd_add_provider_simple(np, pd);
+	cpg_mstp_pd_np = of_node_get(np);
+	cpg_mstp_pd_genpd = pd;
+}
+
+static int __init cpg_mstp_pd_init_provider(void)
+{
+	int error;
+
+	if (!cpg_mstp_pd_np)
+		return -ENODEV;
+
+	error = of_genpd_add_provider_simple(cpg_mstp_pd_np, cpg_mstp_pd_genpd);
+
+	of_node_put(cpg_mstp_pd_np);
+	return error;
 }
+postcore_initcall(cpg_mstp_pd_init_provider);