ALSA: usb-audio: Clean up endpoint setups at PCM prepare

This patch cleans up the superfluous checks and calls for setting up
the endpoints at PCM prepare callback:

- Drop stop_endpoints() and sync_pending_stops() calls; the stream is
  guaranteed to have been already stopped and synced at each PCM
  prepare call by ALSA PCM core

- Call snd_usb_endpoint_prepare() unconditionally;
  the check for endpoint->need_setup is done in
  snd_pcm_hw_endpoint_prepare() itself

- Apply snd_usb_set_format_quirk() only when the endpoint is actually
  set up (i.e. the return code from snd_usb_endpoint_prepare() > 0)

- Move a few lines back into snd_usb_pcm_prepare();
  it's even easier to follow than a small useless function

Link: https://lore.kernel.org/r/20220901130831.6136-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/pcm.c

@@ -433,35 +433,6 @@ static void close_endpoints(struct snd_usb_audio *chip,
 	}
 }
 
-static int configure_endpoints(struct snd_usb_audio *chip,
-			       struct snd_usb_substream *subs)
-{
-	int err;
-
-	if (subs->data_endpoint->need_setup) {
-		/* stop any running stream beforehand */
-		if (stop_endpoints(subs, false))
-			sync_pending_stops(subs);
-		if (subs->sync_endpoint) {
-			err = snd_usb_endpoint_prepare(chip, subs->sync_endpoint);
-			if (err < 0)
-				return err;
-		}
-		err = snd_usb_endpoint_prepare(chip, subs->data_endpoint);
-		if (err < 0)
-			return err;
-		snd_usb_set_format_quirk(subs, subs->cur_audiofmt);
-	} else {
-		if (subs->sync_endpoint) {
-			err = snd_usb_endpoint_prepare(chip, subs->sync_endpoint);
-			if (err < 0)
-				return err;
-		}
-	}
-
-	return 0;
-}
-
 /*
  * hw_params callback
  *
@@ -640,9 +611,18 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 		goto unlock;
 	}
 
-	ret = configure_endpoints(chip, subs);
+	if (subs->sync_endpoint) {
+		ret = snd_usb_endpoint_prepare(chip, subs->sync_endpoint);
+		if (ret < 0)
+			goto unlock;
+	}
+
+	ret = snd_usb_endpoint_prepare(chip, subs->data_endpoint);
 	if (ret < 0)
 		goto unlock;
+	else if (ret > 0)
+		snd_usb_set_format_quirk(subs, subs->cur_audiofmt);
+	ret = 0;
 
 	/* reset the pointer */
 	subs->buffer_bytes = frames_to_bytes(runtime, runtime->buffer_size);