ac/spm: add an assertion to check the number of global instances

To make sure counters aren't silently discarded.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39013>

src/amd/common/ac_spm.c

@@ -545,6 +545,8 @@ bool ac_init_spm(const struct radeon_info *info,
       const struct ac_pc_block *block = ac_pc_get_block(pc, create_info[i].b->gpu_block);
       struct ac_spm_counter_create_info counter = create_info[i];
 
+      assert(block->num_global_instances > 0);
+
       for (unsigned j = 0; j < block->num_global_instances; j++) {
          counter.instance = j;