glsl2: Use linked ir_constant_variable after linking, instead of unlinked.
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 10fd2d5..b2953c6 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1293,7 +1293,7 @@
 	 progress = do_dead_code_local(ir) || progress;
 	 progress = do_dead_code(ir) || progress;
 	 progress = do_tree_grafting(ir) || progress;
-	 progress = do_constant_variable_unlinked(ir) || progress;
+	 progress = do_constant_variable(ir) || progress;
 	 progress = do_constant_folding(ir) || progress;
 	 progress = do_algebraic(ir) || progress;
 	 progress = do_if_return(ir) || progress;