USB: legousbtower: drop unnecessary packed attributes

Drop the packed attributes from the two message structs whose fields
are naturally aligned and do not have any padding.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191105084152.16322-11-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>