Fix host regression on JNI compiler test.

Change-Id: I90556a8201d7a56b5d3467c0d5e17702d58da933
diff --git a/src/assembler_x86.cc b/src/assembler_x86.cc
index 2aae7de..389fc2c 100644
--- a/src/assembler_x86.cc
+++ b/src/assembler_x86.cc
@@ -1589,7 +1589,7 @@
 #if ANDROID_SMP != 0
   EmitUint8(0x0F);  // mfence
   EmitUint8(0xAE);
-  EmitOperand(0, Operand(EAX));  // EAX is unused
+  EmitUint8(0xF0);
 #endif
 }