usb: gadget: u_audio: Subdevice 0 for capture ctls

Both capture and playback alsa devices use subdevice 0. Yet capture-side
ctls are defined for subdevice 1. The patch sets subdevice 0 for them.

Fixes: 02de698ca8 ("usb: gadget: u_audio: add bi-directional volume and mute support")
Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20220105104643.90125-1-pavel.hofman@ivitera.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/u_audio.c

@@ -1147,7 +1147,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 			}
 
 			kctl->id.device = pcm->device;
-			kctl->id.subdevice = i;
+			kctl->id.subdevice = 0;
 
 			err = snd_ctl_add(card, kctl);
 			if (err < 0)
@@ -1170,7 +1170,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 			}
 
 			kctl->id.device = pcm->device;
-			kctl->id.subdevice = i;
+			kctl->id.subdevice = 0;
 
 
 			kctl->tlv.c = u_audio_volume_tlv;