glsl2: Actually use the linked dead code eliminator.

I managed to revert the change from unlinked at some point while
cleaning up the changes.  glsl-fs-raytrace-bug27060 drops from 389
instructions to 370.
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 06f2a82..e7bc700 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1262,7 +1262,7 @@
 	 progress = do_if_simplification(ir) || progress;
 	 progress = do_copy_propagation(ir) || progress;
 	 progress = do_dead_code_local(ir) || progress;
-	 progress = do_dead_code_unlinked(ir) || progress;
+	 progress = do_dead_code(ir) || progress;
 	 progress = do_constant_variable_unlinked(ir) || progress;
 	 progress = do_constant_folding(ir) || progress;
 	 progress = do_if_return(ir) || progress;