qt5: remove GPLv2 license from qt5declarative, qt5script and qt5svg

Since Qt 5.5, those three modules have lost their GPLv2 licensing
option. Remains the LGPLv2.1 with exception and LGPLv3 as the possible
open-source licenses.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>