mesa/glsl: move pixel_center_integer to gl_shader

This is only used by gl_linked_shader as a temp during linking
so use a temp there instead.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -1810,7 +1810,7 @@ set_shader_inout_layout(struct gl_shader *shader,
    case MESA_SHADER_FRAGMENT:
       shader->redeclares_gl_fragcoord = state->fs_redeclares_gl_fragcoord;
       shader->uses_gl_fragcoord = state->fs_uses_gl_fragcoord;
-      shader->info.pixel_center_integer = state->fs_pixel_center_integer;
+      shader->pixel_center_integer = state->fs_pixel_center_integer;
       shader->origin_upper_left = state->fs_origin_upper_left;
       shader->ARB_fragment_coord_conventions_enable =
          state->ARB_fragment_coord_conventions_enable;