opp: Don't print an error if required-opps is missing

The 'required-opps' property is considered optional, hence remove
the pr_err() in of_parse_required_opp() when we find the property is
missing.
While at it, also fix the return value of
of_get_required_opp_performance_state() when of_parse_required_opp()
fails, return a -ENODEV instead of the -EINVAL.
Signed-off-by: NRajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/opp/of.c

@@ -95,15 +95,7 @@ static struct dev_pm_opp *_find_opp_of_np(struct opp_table *opp_table,
 static struct device_node *of_parse_required_opp(struct device_node *np,
 						 int index)
 {
-	struct device_node *required_np;
-
-	required_np = of_parse_phandle(np, "required-opps", index);
-	if (unlikely(!required_np)) {
-		pr_err("%s: Unable to parse required-opps: %pOF, index: %d\n",
-		       __func__, np, index);
-	}
-
-	return required_np;
+	return of_parse_phandle(np, "required-opps", index);
 }
 
 /* The caller must call dev_pm_opp_put_opp_table() after the table is used */
@@ -1327,7 +1319,7 @@ int of_get_required_opp_performance_state(struct device_node *np, int index)
 
 	required_np = of_parse_required_opp(np, index);
 	if (!required_np)
-		return -EINVAL;
+		return -ENODEV;
 
 	opp_table = _find_table_of_opp_np(required_np);
 	if (IS_ERR(opp_table)) {