egl/wayland: use __DRI_IMAGE_PRIME_LINEAR_BUFFER in get_back_bo

Some drivers (radeonsi, iris) relies on this hint to detect DRI_PRIME
blits and implement a special path (eg: SDMA copy for radeonsi).

Reviewed-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27719>
2 files changed