PM / devfreq: passive: Fix get_target_freq when not using required-opp

The 86ad9a2 ("PM / devfreq: Add required OPPs support to passive governor")
supported the required-opp property for using devfreq passive governor.
But, 86ad9a2 has caused the problem on use-case when required-opp
is not used such as exynos-bus.c devfreq driver. So that fix the
get_target_freq of passive governor for supporting the case of when
required-opp is not used.

Fixes: 86ad9a2 ("PM / devfreq: Add required OPPs support to passive governor")
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

Author: chanwoochoi

drivers/devfreq/governor_passive.c

@@ -65,14 +65,15 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
 		dev_pm_opp_put(p_opp);
 
 		if (IS_ERR(opp))
-			return PTR_ERR(opp);
+			goto no_required_opp;
 
 		*freq = dev_pm_opp_get_freq(opp);
 		dev_pm_opp_put(opp);
 
 		return 0;
 	}
 
+no_required_opp:
 	/*
 	 * Get the OPP table's index of decided frequency by governor
 	 * of parent device.