qt5: fix license information for qt5multimedia and qt5xmlpatterns

While most of the Qt5 components indeed seem to be under LGPLv2.1 with
exception, or LGPLv3 or GPLv2, the qt5multimedia and qt5xmlpatterns
components only carry the LGPLv2.1 and LGPLv3 license files, and not
the GPLv2 license file. So one can safely assume that the GPLv2 option
is not available for those components, and this commit adjusts the
<pkg>_LICENSE and <pkg>_LICENSE_FILES variables accordingly.

Fixes:

  http://autobuild.buildroot.org/results/c62/c62eef5e5b8add138cdab34e64103d974d0a510b/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Bernd Kuhls <bernd.kuhls@t-online.de>