opp: remove WARN when no valid OPPs remain

This WARN can be triggered per-core and the stack trace is not useful.
Replace it with plain dev_err(). Fix a comment while at it.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/of.c

@@ -964,8 +964,9 @@ static int _of_add_opp_table_v2(struct device *dev, struct opp_table *opp_table)
 		}
 	}
 
-	/* There should be one of more OPP defined */
-	if (WARN_ON(!count)) {
+	/* There should be one or more OPPs defined */
+	if (!count) {
+		dev_err(dev, "%s: no supported OPPs", __func__);
 		ret = -ENOENT;
 		goto remove_static_opp;
 	}