Fixes ARM multiplication instruction version checking.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
===================================================================
--- runtime/vm/assembler_arm.h	(revision 44897)
+++ runtime/vm/assembler_arm.h	(working copy)
@@ -438,9 +438,12 @@
              Condition cond = AL);
   void umlal(Register rd_lo, Register rd_hi, Register rn, Register rm,
              Condition cond = AL);
-  void umaal(Register rd_lo, Register rd_hi, Register rn, Register rm,
-             Condition cond = AL);
 
+  // Emulation of this instruction uses IP and the condition codes. Therefore,
+  // none of the registers can be IP, and the instruction can only be used
+  // unconditionally.
+  void umaal(Register rd_lo, Register rd_hi, Register rn, Register rm);
+
   // Division instructions.
   void sdiv(Register rd, Register rn, Register rm, Condition cond = AL);
   void udiv(Register rd, Register rn, Register rm, Condition cond = AL);