usb: yurex: Fix inconsistent locking bug in yurex_read()

Unlock before returning on the error path.

Fixes: 86b20af11e84 ("usb: yurex: Replace snprintf() with the safer scnprintf() variant")
Reported-by: Dan Carpenter <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/r/[e-mail]/
Signed-off-by: Harshit Mogalapalli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/yurex.c

···
 		return -ENODEV;
 	}
 
-	if (WARN_ON_ONCE(dev->bbu > S64_MAX || dev->bbu < S64_MIN))
+	if (WARN_ON_ONCE(dev->bbu > S64_MAX || dev->bbu < S64_MIN)) {
+		mutex_unlock(&dev->io_mutex);
 		return -EIO;
+	}
 
 	spin_lock_irqsave(&dev->lock, flags);
 	scnprintf(in_buffer, MAX_S64_STRLEN, "%lld\n", dev->bbu);