MIPS: Fix NaN tests.

test/mjsunit/regress/regress-undefined-nan.js

Index: test/mjsunit/regress/regress-undefined-nan.js
diff --git a/test/mjsunit/regress/regress-undefined-nan.js b/test/mjsunit/regress/regress-undefined-nan.js
index 93106c5eb17522afef4eae47a4d1f6677dcc8e1f..0e9b3d3f4a12bba68ec2380eac985a94f75b4875 100644
--- a/test/mjsunit/regress/regress-undefined-nan.js
+++ b/test/mjsunit/regress/regress-undefined-nan.js
@@ -10,8 +10,8 @@ function loader(dst, src, i) {
 
 var ab = new ArrayBuffer(8);
 var i_view = new Int32Array(ab);
-i_view[0] = 0xFFF7FFFF;
-i_view[1] = 0xFFF7FFFF;
+i_view[0] = %GetHoleNaNUpper()
+i_view[1] = %GetHoleNaNLower();
 var f_view = new Float64Array(ab);
 
 var fixed_double_elements = new Float64Array(1);