freedreno/gmem: Fix col0 calc
Fix typo in calculation of position of start of a row of tiles. This could otherwise cause an out-of-bounds access in the next patch. Fixes: 81d85be9 freedreno/gmem: Reverse order of alternative tile rows Signed-off-by:Rob Clark <robdclark@chromium.org> Part-of: <mesa/mesa!17888>