Render DRM-PRIME frames as opaque images

We can't always assume they are NV12. Even if they _are_ NV12,
they may have DRM format modifiers that are incompatible with
simply assuming linear Y and UV buffers (such as tiling).

app/streaming/video/ffmpeg-renderers/drm.h

@@ -35,6 +35,7 @@ private:
     SDL_Rect m_OutputRect;
 
 #ifdef HAVE_EGL
+    bool m_EGLExtDmaBuf;
     PFNEGLCREATEIMAGEPROC m_eglCreateImage;
     PFNEGLDESTROYIMAGEPROC m_eglDestroyImage;
     PFNEGLCREATEIMAGEKHRPROC m_eglCreateImageKHR;