qtbase: Do not pin gles2 when using open source graphic stack
One of the advantages in using upstream mesa is that we have the freedom to
use gl or gles2 for qtbase. So follow meta-qt5's default here which is
desktop-gl and give other layers a more simple chance to change default if
necessary.
Notes:
* Did performance tests with my images and did not find any performance
issues.
* Some recipes in meta-qt5-extra fail to build when qtbase is build for gles2.
A patch addressing imx was applied [1] - but honestly it is not the way to
go: use meta-qt5's default which is fine.
[1] https://github.com/schnitzeltony/meta-qt5-extra/commit/
0972828deb6a9e6a44d7596e6e4817fd74dbb51c
Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
