PM / Domains: Do not print PM domain add error message if EPROBE_DEFER

EPROBE_DEFER is not an error, hence printing an error message like

    renesas_irqc e61c0000.interrupt-controller: failed to add to PM domain always-on: -517

may confuse the user.

Suppress the error message in case of EPROBE_DEFER to fix this.
Reported-by: NYoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NSimon Horman <horms+renesas@verge.net.au>
Acked-by: NKevin Hilman <khilman@baylibre.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/domain.c

@@ -2031,8 +2031,9 @@ int genpd_dev_pm_attach(struct device *dev)
 	mutex_unlock(&gpd_list_lock);
 
 	if (ret < 0) {
-		dev_err(dev, "failed to add to PM domain %s: %d",
-			pd->name, ret);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "failed to add to PM domain %s: %d",
+				pd->name, ret);
 		goto out;
 	}