ART: Even more Quick cleanup

Remove Backend.

Change-Id: I247cc65ccda6a362ba1a8f5e73e7f12ecd980a87
diff --git a/compiler/dex/compiler_ir.cc b/compiler/dex/compiler_ir.cc
index 0cfa966..7fc1b03 100644
--- a/compiler/dex/compiler_ir.cc
+++ b/compiler/dex/compiler_ir.cc
@@ -18,8 +18,8 @@
 
 #include "arch/instruction_set_features.h"
 #include "base/dumpable.h"
-#include "backend.h"
 #include "dex_flags.h"
+#include "dex/quick/mir_to_lir.h"
 #include "driver/compiler_driver.h"
 #include "mir_graph.h"