Remove the old ARM code generator from ART's Optimizing compiler.

The AArch32 VIXL-based code generator has been the default
ARM code generator in ART for some time now. The old ARM
code generator does not compile anymore; retiring it.

Test: test.py
Bug: 63316036
Change-Id: Iab8fbc4ac73eac2c1a809cd7b22fec6b619755db
diff --git a/compiler/optimizing/code_generator.cc b/compiler/optimizing/code_generator.cc
index 93234f9..2872cf7 100644
--- a/compiler/optimizing/code_generator.cc
+++ b/compiler/optimizing/code_generator.cc
@@ -17,7 +17,6 @@
 #include "code_generator.h"
 
 #ifdef ART_ENABLE_CODEGEN_arm
-#include "code_generator_arm.h"
 #include "code_generator_arm_vixl.h"
 #endif
 
@@ -627,19 +626,11 @@
 #ifdef ART_ENABLE_CODEGEN_arm
     case kArm:
     case kThumb2: {
-      if (kArmUseVIXL32) {
-        return std::unique_ptr<CodeGenerator>(
-            new (arena) arm::CodeGeneratorARMVIXL(graph,
-                                                  *isa_features.AsArmInstructionSetFeatures(),
-                                                  compiler_options,
-                                                  stats));
-      } else {
-          return std::unique_ptr<CodeGenerator>(
-            new (arena) arm::CodeGeneratorARM(graph,
-                                              *isa_features.AsArmInstructionSetFeatures(),
-                                              compiler_options,
-                                              stats));
-      }
+      return std::unique_ptr<CodeGenerator>(
+          new (arena) arm::CodeGeneratorARMVIXL(graph,
+                                                *isa_features.AsArmInstructionSetFeatures(),
+                                                compiler_options,
+                                                stats));
     }
 #endif
 #ifdef ART_ENABLE_CODEGEN_arm64