gstreamer1.0-plugins-bad: Remove useless overrides

The PACKAGECONFIG_GL has the same value as the provided
by the recipe, by default. This removes this duplication.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
imx-base: Include gstreamer1.0-plugins-imx for i.MX6Q and i.MX6DL

libfslvpuwrap is only available for i.MX6Q and i.MX6DL. This makes
gstreamer1.0-plugins-imx unusable on other i.MX6 SoC familes and this
commit updates the default setting accordingly.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
piglit: Add a dependency over virtual/egl

The build system can also use egl when GL is not avail so we ought to
add this to the dependency chain as gpu-viv-bin-mx6q would not be
included otherwise, for i.MX6SL.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>