qt5/qtwebsocket: remove GPLv2 license

This module loose his GPLv2 licensing option. Remains the LGPLv2.1 with
exception and LGPLv3 as the possible open-source licenses.

Fixes:
http://autobuild.buildroot.net/results/6c80ba0669a7fc8cc60baaa849044fd65a78ce87/


Signed-off-by: Julien Corjon <corjon.j@ecagroup.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>