Revert of Remove register index/code indirection

src/arm64/constants-arm64.h

Index: src/arm64/constants-arm64.h
diff --git a/src/arm64/constants-arm64.h b/src/arm64/constants-arm64.h
index b419a6e85668e6fc503c96cf5c4491607ab9c7e0..1529c647ff75c8ce6a81b5b94a82c9161b402da1 100644
--- a/src/arm64/constants-arm64.h
+++ b/src/arm64/constants-arm64.h
@@ -118,6 +118,12 @@
 const unsigned kFloatMantissaBits = 23;
 const unsigned kFloatExponentBits = 8;
 
+#define REGISTER_CODE_LIST(R)                                                  \
+R(0)  R(1)  R(2)  R(3)  R(4)  R(5)  R(6)  R(7)                                 \
+R(8)  R(9)  R(10) R(11) R(12) R(13) R(14) R(15)                                \
+R(16) R(17) R(18) R(19) R(20) R(21) R(22) R(23)                                \
+R(24) R(25) R(26) R(27) R(28) R(29) R(30) R(31)
+
 #define INSTRUCTION_FIELDS_LIST(V_)                                            \
 /* Register fields */                                                          \
 V_(Rd, 4, 0, Bits)                        /* Destination register.     */      \