PM / OPP: Don't WARN on multiple calls to dev_pm_opp_set_regulators()

If a platform specific OPP driver has called this routine first and set
the regulators, then the second call from cpufreq-dt driver will hit the
WARN_ON(). Remove the WARN_ON(), but continue to return error in such
cases.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/opp/core.c

@@ -1485,7 +1485,7 @@ struct opp_table *dev_pm_opp_set_regulators(struct device *dev,
 	}
 
 	/* Already have regulators set */
-	if (WARN_ON(opp_table->regulators)) {
+	if (opp_table->regulators) {
 		ret = -EBUSY;
 		goto err;
 	}