This code path is used when frames are rendered as textures through
GstVideoGLTextureUploadMeta with EGL, mainly under Wayland.

Oringally the EGLImage was exported as GEM, which was handled by
the intel-vaapi-driver, but gallium cannot create VA surfaces from
GEM buffers, breaking the decoding.

This patch replace the exporting of EGLImages from GEM to DMABuf.

DMABuf is well handled either by intel-vaapi-driver and gallium.

Fixes: #137