USB: legotower: fix logical error in recent commit

Commit d9f0d82f

 ("USB: legousbtower: use usb_control_msg_recv()")
contained an elementary logical error.  The check of the return code
from the new usb_control_msg_recv() function was inverted.

Reported-and-tested-by:  <syzbot+9be25235b7a69b24d117@syzkaller.appspotmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20201208163042.GD1298255@rowland.harvard.edu
Fixes: d9f0d82f

 ("USB: legousbtower: use usb_control_msg_recv()")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>