soc: imx: gpcv2: fix regulator deferred probe

If a regulator requests a deferred probe, the power domain gets
initialized twice. This leads to a list double add (without
list debugging the kernel hangs due to the double add later):

WARNING: CPU: 0 PID: 19 at lib/list_debug.c:31 __list_add_valid+0xbc/0xc4
list_add double add: new=c1229754, prev=c12383b4, next=c1229754.

Initialize the power domain after we get the regulator. Also do
not print an error in case the regulator defers probing.

Cc: Fabio Estevam <[e-mail]>
Cc: Andrey Smirnov <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Fixes: 03aa12629fc4 ("soc: imx: Add GPCv2 power gating driver")
Signed-off-by: Stefan Agner <[e-mail]>
Acked-by: Andrey Smirnov <[e-mail]>
Tested-by: Andrey Smirnov <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

drivers/soc/imx/gpcv2.c

···
 
 	domain->dev = &pdev->dev;
 
-	ret = pm_genpd_init(&domain->genpd, NULL, true);
-	if (ret) {
-		dev_err(domain->dev, "Failed to init power domain\n");
-		return ret;
-	}
-
 	domain->regulator = devm_regulator_get_optional(domain->dev, "power");
 	if (IS_ERR(domain->regulator)) {
 		if (PTR_ERR(domain->regulator) != -ENODEV) {
-			dev_err(domain->dev, "Failed to get domain's regulator\n");
+			if (PTR_ERR(domain->regulator) != -EPROBE_DEFER)
+				dev_err(domain->dev, "Failed to get domain's regulator\n");
 			return PTR_ERR(domain->regulator);
 		}
 	} else {
 		regulator_set_voltage(domain->regulator,
 				      domain->voltage, domain->voltage);
+	}
+
+	ret = pm_genpd_init(&domain->genpd, NULL, true);
+	if (ret) {
+		dev_err(domain->dev, "Failed to init power domain\n");
+		return ret;
 	}
 
 	ret = of_genpd_add_provider_simple(domain->dev->of_node,