Clean up kOpCmp on ARM.

kThumb2CmnRI8M is now used.

Change-Id: I300299258ed99d86c300dee45c904c360dd44638
diff --git a/disassembler/disassembler_arm.cc b/disassembler/disassembler_arm.cc
index db51fab..936fb07 100644
--- a/disassembler/disassembler_arm.cc
+++ b/disassembler/disassembler_arm.cc
@@ -854,7 +854,7 @@
           } else if (op3 == 0x4) {
             opcode << "teq";
           } else if (op3 == 0x8) {
-            opcode << "cmw";
+            opcode << "cmn.w";
           } else {
             opcode << "cmp.w";
           }