radv: Implement cosited_even sampling.
Apparently cosited_even was the required one instead of midpoint. This adds slight offset of 0.5 pixels to the coordinates (+ we need the image size to convert to normalized coords) Fixes: 91702374 "radv: Add ycbcr lowering pass." Acked-by:Samuel Pitoiset <samuel.pitoiset@gmail.com> (cherry picked from commit 56923512)