This pool isn't reusing its buffers, which makes it pointless to enable
the cache
Holding an extra buffer in free queue can also lead to a deadlock when
the pool's max buffer count is configured low (commonly 2).
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8939>
* if downstream provides us with a pool that can allocate DMA buffers,
gldownload wraps it into a GL buffer pool that uses
glEGLImageTargetTexture2DOES() to import dmabuf into textures
* upstream GL elements can allocate from that pool
* gldownload unwraps DMA buffers from incoming GL buffers and passes
them downstream
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6792>
