ac/surface: fix valgrind warnings in DCC retile tile lookups

ac/surface: fix valgrind warnings in DCC retile tile lookups

==12920== Conditional jump or move depends on uninitialised value(s)
==12920==    at 0x8F39391: util_fast_urem32 (fast_urem_by_const.h:71)
==12920==    by 0x8F39391: hash_table_search (hash_table.c:285)
==12920==    by 0x8B06D5D: ac_compute_dcc_retile_tile_indices (ac_surface.c:136)

Fixes: a37aeb128d5f7c "amd/common: Cache intra-tile addresses for retile map."

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7055>