Fix typo in ISA centralization

X86 needs sign-extension.

Change-Id: I1253fbc9aa0e732e37b976a0723ec89155e7e2e7
diff --git a/compiler/jni/quick/jni_compiler.cc b/compiler/jni/quick/jni_compiler.cc
index e03aefb..93b1b5a 100644
--- a/compiler/jni/quick/jni_compiler.cc
+++ b/compiler/jni/quick/jni_compiler.cc
@@ -314,7 +314,7 @@
           mr_conv->InterproceduralScratchRegister());
 
   // 10. Fix differences in result widths.
-  if (is_64_bit_target) {
+  if (instruction_set == kX86 || instruction_set == kX86_64) {
     if (main_jni_conv->GetReturnType() == Primitive::kPrimByte ||
         main_jni_conv->GetReturnType() == Primitive::kPrimShort) {
       __ SignExtend(main_jni_conv->ReturnRegister(),