glsl: Add a new ir_txs (textureSize) opcode to ir_texture.

One unique aspect of TXS is that it doesn't have a coordinate.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/glsl/opt_tree_grafting.cpp

@@ -258,6 +258,7 @@ ir_tree_grafting_visitor::visit_enter(ir_texture *ir)
       break;
    case ir_txf:
    case ir_txl:
+   case ir_txs:
       if (do_graft(&ir->lod_info.lod))
 	 return visit_stop;
       break;