testing/ffmpeg-v4l2-request: new aport

This MR is packaging ffmpeg fork, which is adding hardware video decoders support, found on some Rockchip SoCs, by enabling ffmpeg to use HW decoder via V4L2 kernel interface (https://wiki.pine64.org/wiki/Mainline_Hardware_Decoding for more details).

Adding this is beneficial for good user experience while using Moonlight streaming on these devices, since pretty big part of them are various Chinese cheaper handheld gaming consoles.