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 <[e-mail]>
Reviewed-by: Stephen Boyd <[e-mail]>
Tested-by: Dave Gerlach <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/base/power/opp/core.c

···
 	}
 
 	/* Already have regulators set */
-	if (WARN_ON(opp_table->regulators)) {
+	if (opp_table->regulators) {
 		ret = -EBUSY;
 		goto err;
 	}