Add MLA instruction to ARM integerated assembler.

src/IceInstARM32.h

Index: src/IceInstARM32.h
diff --git a/src/IceInstARM32.h b/src/IceInstARM32.h
index 28317d270f13cff97b6dd338fe31fe0855d48c4b..e8ed5819a02501b046dbada78a6717dbe123bc65 100644
--- a/src/IceInstARM32.h
+++ b/src/IceInstARM32.h
@@ -674,6 +674,7 @@ public:
       return;
     emitFourAddr(Opcode, this, Func);
   }
+  void emitIAS(const Cfg *Func) const override;
   void dump(const Cfg *Func) const override {
     if (!BuildDefs::dump())
       return;