i965: stop depending on gl_shader_program for brw_compute_vue_map() params

This removes another dependency on gl_shader_program from the codegen functions,
this will help allow us to use gl_program for the CurrentProgram array rather
than gl_shader_program.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
diff --git a/src/mesa/drivers/dri/i965/brw_gs.c b/src/mesa/drivers/dri/i965/brw_gs.c
index 76ceb5b..7886737 100644
--- a/src/mesa/drivers/dri/i965/brw_gs.c
+++ b/src/mesa/drivers/dri/i965/brw_gs.c
@@ -134,7 +134,7 @@
 
    brw_compute_vue_map(devinfo,
                        &prog_data.base.vue_map, outputs_written,
-                       prog->SeparateShader);
+                       gp->program.info.separate_shader);
 
    int st_index = -1;
    if (INTEL_DEBUG & DEBUG_SHADER_TIME)