qt: Unbreak build with qt-egl enabled but viv_fb missing
Avoids an error message when the feature is explicitly enabled:
ERROR: Feature qt-egl cannot be enabled: gstreamer-gl-viv_fb-1.0 is required
Avoids an error message when the feature is explicitly enabled:
ERROR: Feature qt-egl cannot be enabled: gstreamer-gl-viv_fb-1.0 is required