turnip: Remove unsigned nonnegative check.

index is of type uint32_t.

Fix defect reported by Coverity Scan.

Macro compares unsigned to 0 (NO_EFFECT)
unsigned_compare: This greater-than-or-equal-to-zero comparison of
an unsigned value is always true. index >= 0U.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8231>

src/freedreno/vulkan/tu_query.c

@@ -202,8 +202,6 @@ perfcntr_index(const struct fd_perfcntr_group *group, uint32_t group_count,
          break;
       }
       index -= group[i].num_countables;
-
-      assert(index >= 0);
    }
 
    assert(i < group_count);