ALSA: core, oxygen, virtuoso: add an enum control info helper

Introduce the helper function snd_ctl_enum_info() to fill out the
elem_info fields for an enumerated control.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/oxygen/xonar_cs43xx.c

@@ -298,13 +298,7 @@ static int rolloff_info(struct snd_kcontrol *ctl,
 		"Fast Roll-off", "Slow Roll-off"
 	};
 
-	info->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED;
-	info->count = 1;
-	info->value.enumerated.items = 2;
-	if (info->value.enumerated.item >= 2)
-		info->value.enumerated.item = 1;
-	strcpy(info->value.enumerated.name, names[info->value.enumerated.item]);
-	return 0;
+	return snd_ctl_enum_info(info, 1, 2, names);
 }
 
 static int rolloff_get(struct snd_kcontrol *ctl,