freedreno/a6xx: set CHROMA_LINEAR and CHROMA_LOCATION_MIDPOINT
This is closer to what the blob does on a618 and a635 (except the blob does not set CHROMA_LINEAR
on a618).
The main thing I need is CHROMA_LINEAR
on a635. It fixes android.media.cts.DecodeAccuracyTest#*
on a635.
Setting CHROMA_LOCATION_MIDPOINT
seems to improve the image quality.