drm/nouveau/pm: fix missing volt changes when boot voltage is undefined

Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/nouveau_pm.c

···
 	}
 
 	if (pm->voltage.supported && pm->voltage_set) {
-		if (a->volt_min && b->volt_min && b->volt_min > a->volt_min) {
+		if (perflvl->volt_min && b->volt_min > a->volt_min) {
 			ret = pm->voltage_set(dev, perflvl->volt_min);
 			if (ret) {
 				NV_ERROR(dev, "voltage set failed: %d\n", ret);