backends/drm: set dma-fence deadlines if available
This tells the kernel when a buffer should be done rendering, which allows it to for example increase GPU clocks in order to hopefully hit our deadlines. That in turn should reduce the amount of dropped frames
Draft because the uAPI isn't actually merged to the kernel yet. See https://lists.freedesktop.org/archives/dri-devel/2023-August/419773.html for the needed patches
cc #124
Edited by Xaver Hugl