[ALSA] Fix hang-up at disconnection of usb-audio

Fix hang-up at disconnection of usb-audio devices while accessing PCM.
Don't handle PCM operations any more after shutdown flag is set.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 37b4b10..66e24b5 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -1310,7 +1310,8 @@
 			       int f_flags)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 	if (snd_pcm_running(substream))
 		return -EBUSY;
@@ -1568,7 +1569,8 @@
 	runtime = substream->runtime;
 	card = substream->pcm->card;
 
-	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
+	if (runtime->status->state == SNDRV_PCM_STATE_OPEN ||
+	    runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
 
 	snd_power_lock(card);