ALSA: vmaster: use position offset macro of TLV data

A series of SNDRV_CTL_TLVO_XXX macro was introduced for position offset
of TLV data. This commit applies a code optimization.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/vmaster.c

@@ -421,13 +421,15 @@ struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
 	kctl->private_free = master_free;
 
 	/* additional (constant) TLV read */
-	if (tlv &&
-	    (tlv[0] == SNDRV_CTL_TLVT_DB_SCALE ||
-	     tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX ||
-	     tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX_MUTE)) {
-		kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
-		memcpy(master->tlv, tlv, sizeof(master->tlv));
-		kctl->tlv.p = master->tlv;
+	if (tlv) {
+		unsigned int type = tlv[SNDRV_CTL_TLVO_TYPE];
+		if (type == SNDRV_CTL_TLVT_DB_SCALE ||
+		    type == SNDRV_CTL_TLVT_DB_MINMAX ||
+		    type == SNDRV_CTL_TLVT_DB_MINMAX_MUTE) {
+			kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
+			memcpy(master->tlv, tlv, sizeof(master->tlv));
+			kctl->tlv.p = master->tlv;
+		}
 	}
 
 	return kctl;