ilo: silence a compiler warning

Silence

  ilo_query.c:120:7: warning: 'return' with no value, in function returning non-void

since commit 96f164f6.

src/gallium/drivers/ilo/ilo_query.c

@@ -117,7 +117,7 @@ ilo_begin_query(struct pipe_context *pipe, struct pipe_query *query)
    struct ilo_query *q = ilo_query(query);
 
    if (q->active)
-      return;
+      return false;
 
    util_query_clear_result(&q->result, q->type);
    q->used = 0;