ALSA: drivers: opl3: fix useless self-comparison

Sparse throws the following warning:

sound/drivers/opl3/opl3_midi.c:183:60: error: self-comparison always
evaluates to false

This is likely a 16+ year old confusion between vp2 and vp.
Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210526192957.449515-1-pierre-louis.bossart@linux.intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/opl3/opl3_midi.c

@@ -180,8 +180,7 @@ static int opl3_get_voice(struct snd_opl3 *opl3, int instr_4op,
 			if (vp2->state == SNDRV_OPL3_ST_ON_2OP) {
 				/* kill two voices, EXPENSIVE */
 				bp++;
-				voice_time = (voice_time > vp->time) ?
-					voice_time : vp->time;
+				voice_time = max(voice_time, vp2->time);
 			}
 		} else {
 			/* allocate 2op voice */