Use ATTRIBUTE_UNUSED more.

Use it in lieu of UNUSED(), which had some incorrect uses.

Change-Id: If247dce58b72056f6eea84968e7196f0b5bef4da
diff --git a/compiler/dex/quick/x86/assemble_x86.cc b/compiler/dex/quick/x86/assemble_x86.cc
index 12523ac..64becb9 100644
--- a/compiler/dex/quick/x86/assemble_x86.cc
+++ b/compiler/dex/quick/x86/assemble_x86.cc
@@ -1629,8 +1629,8 @@
  * instruction.  In those cases we will try to substitute a new code
  * sequence or request that the trace be shortened and retried.
  */
-AssemblerStatus X86Mir2Lir::AssembleInstructions(LIR* first_lir_insn, CodeOffset start_addr) {
-  UNUSED(start_addr);
+AssemblerStatus X86Mir2Lir::AssembleInstructions(LIR* first_lir_insn,
+                                                 CodeOffset start_addr ATTRIBUTE_UNUSED) {
   LIR *lir;
   AssemblerStatus res = kSuccess;  // Assume success