freedreno/ir3: Demote centroid usage to pixel on non-msaa.

freedreno/ir3: Demote centroid usage to pixel on non-msaa.

Like with the sample qualifier on all GPUs, use pixel on older HW when
MSAA rasterization is disabled to get reliable results.  Since I ran many
CI jobs on this, this updates the A530 TF flakes list, though I don't
think that this MR necessarily made it flakier (we were already struggling
on a5xx TF, which was what was motivating me to look at this!)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9641>