ac/surface: Fix GFX9 sparse mip offset.
Used the wrong offset.
Fixes: 50bafb85 ("ac/surf: Add sparse texture info to radeon_surf.") Closes: #4072 (closed)
Used the wrong offset.
Fixes: 50bafb85 ("ac/surf: Add sparse texture info to radeon_surf.") Closes: #4072 (closed)