nir: Constify nir_gs_count_vertices

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/nir/nir.h

@@ -1899,7 +1899,7 @@ void nir_dump_dom_frontier(nir_shader *shader, FILE *fp);
 void nir_dump_cfg_impl(nir_function_impl *impl, FILE *fp);
 void nir_dump_cfg(nir_shader *shader, FILE *fp);
 
-int nir_gs_count_vertices(nir_shader *shader);
+int nir_gs_count_vertices(const nir_shader *shader);
 
 bool nir_split_var_copies(nir_shader *shader);
 

src/glsl/nir/nir_gs_count_vertices.c

@@ -51,7 +51,7 @@ as_set_vertex_count(nir_instr *instr)
  * counting at the NIR level.
  */
 int
-nir_gs_count_vertices(nir_shader *shader)
+nir_gs_count_vertices(const nir_shader *shader)
 {
    int count = -1;