freedreno/a6xx: Fix UBWC blockheight for RG8.

Using texturator on a P3A at 1024x1024, RG8 has log2w/h of 6x7 instead of
R16I/UI's 6x8.  The other blockw/h I verified other than cpp=1
(R8/R8I/R8UI didn't use UBWC) and 32 (would need a bigger type).

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4931>
1 file changed