intel/perf: Fix unused var warning in release builds.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5829>
diff --git a/src/intel/perf/gen_perf.c b/src/intel/perf/gen_perf.c
index 26dc497..f31b15a 100644
--- a/src/intel/perf/gen_perf.c
+++ b/src/intel/perf/gen_perf.c
@@ -866,7 +866,7 @@
                              struct gen_perf_counter_pass *counter_pass)
 {
    uint64_t queries_mask = get_passes_mask(perf, counter_indices, counter_indices_count);
-   uint32_t n_passes = __builtin_popcount(queries_mask);
+   ASSERTED uint32_t n_passes = __builtin_popcount(queries_mask);
 
    for (uint32_t i = 0; i < counter_indices_count; i++) {
       assert(counter_indices[i] < perf->n_counters);