Fix for the HIP build+test errors introduced by the ndtri support.

The fixes needed are
 * adding EIGEN_DEVICE_FUNC attribute to a couple of funcs (else HIPCC will error out when non-device funcs are called from global/device funcs)
 * switching to using ::<math_func> instead std::<math_func> (only for HIPCC) in cases where the std::<math_func> is not recognized as a device func by HIPCC
 * removing an errant "j" from a testcase (don't know how that made it in to begin with!)

unsupported/Eigen/src/SpecialFunctions/SpecialFunctionsImpl.h

@@ -624,6 +624,7 @@ EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T generic_ndtri_lt_exp_neg_two(
 }
 
 template <typename T, typename ScalarType>
+EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
 T generic_ndtri(const T& a) {
   const T maxnum = pset1<T>(NumTraits<ScalarType>::infinity());
   const T neg_maxnum = pset1<T>(-NumTraits<ScalarType>::infinity());