ac/spm: fix checking if the counter instance is valid

This should be compared against the number of global instances, and
there is also an off-by-one error.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25211>

src/amd/common/ac_spm.c

@@ -240,7 +240,7 @@ ac_spm_add_counter(const struct ac_perfcounters *pc,
    }
 
    /* Check if the number of instances is valid. */
-   if (info->b->instance > block->num_instances) {
+   if (info->b->instance > block->num_global_instances - 1) {
       fprintf(stderr, "ac/spm: Invalid instance ID.\n");
       return false;
    }