ALSA: emu10k1: remove unused emu->pcm_playback_efx_substream field

Amends historic commit 27ae958c ("emu10k1 driver - add multichannel
device hw:x,3 [2-8/8]").
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230422132430.1057468-2-oswald.buddenhagen@gmx.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/emu10k1.h

@@ -1764,7 +1764,6 @@ struct snd_emu10k1 {
 	struct snd_pcm_substream *pcm_capture_substream;
 	struct snd_pcm_substream *pcm_capture_mic_substream;
 	struct snd_pcm_substream *pcm_capture_efx_substream;
-	struct snd_pcm_substream *pcm_playback_efx_substream;
 
 	struct snd_timer *timer;
 

sound/pci/emu10k1/emupcm.c

@@ -1044,8 +1044,6 @@ static int snd_emu10k1_efx_playback_open(struct snd_pcm_substream *substream)
 	epcm->type = PLAYBACK_EFX;
 	epcm->substream = substream;
 	
-	emu->pcm_playback_efx_substream = substream;
-
 	runtime->private_data = epcm;
 	runtime->private_free = snd_emu10k1_pcm_free_substream;
 	runtime->hw = snd_emu10k1_efx_playback;