ARM/ARM64: Clean up Baker RB introspection codegen.

Remove the guard flags and remove unused code.

Avoid unnecessary temporaries for JIT. This was missed in
    https://android-review.googlesource.com/725705

Test: m test-art-host-gtest
Test: Pixel 2 XL boots.
Test: m test-art-target-gtest
Test: testrunner.py --target --optimizing --jit
Bug: 36141117
Change-Id: Ic1bdc640db3f18d7169b0e62644f190e65a98d38
diff --git a/compiler/optimizing/code_generator_arm_vixl.h b/compiler/optimizing/code_generator_arm_vixl.h
index ef82f2e..0106236 100644
--- a/compiler/optimizing/code_generator_arm_vixl.h
+++ b/compiler/optimizing/code_generator_arm_vixl.h
@@ -632,8 +632,7 @@
                                              bool needs_null_check);
   // Fast path implementation of ReadBarrier::Barrier for a heap
   // reference array load when Baker's read barriers are used.
-  void GenerateArrayLoadWithBakerReadBarrier(HInstruction* instruction,
-                                             Location ref,
+  void GenerateArrayLoadWithBakerReadBarrier(Location ref,
                                              vixl::aarch32::Register obj,
                                              uint32_t data_offset,
                                              Location index,