Rename current register allocator implementation

This will allow a cleaner commit in an upcoming
refactoring of register allocation.

Test: m test-art-host

Change-Id: If420c97b088b3c934411ff83373e024003120746
diff --git a/compiler/optimizing/codegen_test.cc b/compiler/optimizing/codegen_test.cc
index 6be79fa..6f487c5 100644
--- a/compiler/optimizing/codegen_test.cc
+++ b/compiler/optimizing/codegen_test.cc
@@ -44,7 +44,7 @@
 #include "nodes.h"
 #include "optimizing_unit_test.h"
 #include "prepare_for_register_allocation.h"
-#include "register_allocator.h"
+#include "register_allocator_linear_scan.h"
 #include "ssa_liveness_analysis.h"
 #include "utils.h"
 #include "utils/arm/managed_register_arm.h"