ALSA: core: remove redundant spin_lock pair in snd_card_disconnect

[ Upstream commit abc21649b3e5c34b143bf86f0c78e33d5815e250 ]

modification in commit 2a3f7221acdd ("ALSA: core: Fix card races between
register and disconnect") resulting in this problem.

Fixes: 2a3f7221acdd ("ALSA: core: Fix card races between register and disconnect")
Signed-off-by: Jia Zhou <zhou.jia2@zte.com.cn>
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Link: https://lore.kernel.org/r/1616989007-34429-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

sound/core/init.c

@@ -404,10 +404,8 @@ int snd_card_disconnect(struct snd_card *card)
 		return 0;
 	}
 	card->shutdown = 1;
-	spin_unlock(&card->files_lock);
 
 	/* replace file->f_op with special dummy operations */
-	spin_lock(&card->files_lock);
 	list_for_each_entry(mfile, &card->files_list, list) {
 		/* it's critical part, use endless loop */
 		/* we have no room to fail */