ALSA: usb-audio: Pass JOINT_DUPLEX info flag for implicit fb streams

When a stream is in the implicit feedback mode, it's more or less tied
with a capture stream.  Passing SNDRV_PCM_INFO_JOINT_DUPLEX may help
for user-space to understand the situation.

Link: https://lore.kernel.org/r/20211007083528.4184-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/pcm.c

@@ -1080,6 +1080,13 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
 	if (err < 0)
 		return err;
 
+	list_for_each_entry(fp, &subs->fmt_list, list) {
+		if (fp->implicit_fb) {
+			runtime->hw.info |= SNDRV_PCM_INFO_JOINT_DUPLEX;
+			break;
+		}
+	}
+
 	return 0;
 }