The latest generation video decoder on the Turing chips supports
decoding HEVC 4:4:4. Supporting this is relatively straight-forward;
we need to account for the different chroma format and pick the
right output and sw formats at the right times.

There was one bug which was the hard-coded assumption that the
first chroma plane would be half-height; I fixed this to use the
actual shift value on the plane.

We also need to pass the SPS and PPS range extension flags.