USB: legousbtower: drop redundant MODULE_LICENSE ifdef

The MODULE_LICENSE macro is unconditionally defined in module.h, no need
to ifdef its use.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191105084152.16322-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>