The ff400_copy_msg_to_user() function drops the spin lock to call
copy_to_user().  However, if the copy_to_user() fails, then it must
take the lock again before returning.  Failure to take the lock leads
to a double unlock in the caller, hwdep_read().

Fixes: acdebd8b ("ALSA: fireface: implement message parser for Fireface 400")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/Y8at+W/7OGvEBY8O@kiliSigned-off-by: Takashi Iwai <tiwai@suse.de>