buildroot

libuci: update legal info

CLI tool and lua bindings are released under GPLv2.

Reviewed-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Signed-off-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
[Thomas: use proper construct to concatenate new licenses to
<pkg>_LICENSE, as suggested by Yann E. Morin.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>