This commit contains the following (HIP specific) updates:

- unsupported/Eigen/CXX11/src/Tensor/TensorReductionGpu.h
  Changing "pass-by-reference" argument to be "pass-by-value" instead
  (in a  __global__ function decl).
  "pass-by-reference" arguments to __global__ functions are unwise,
  and will be explicitly flagged as errors by the newer versions of HIP.

- Eigen/src/Core/util/Memory.h
- unsupported/Eigen/CXX11/src/Tensor/TensorContraction.h
  Changes introduced in recent commits breaks the HIP compile.
  Adding EIGEN_DEVICE_FUNC attribute to some functions and
  calling ::malloc/free instead of the corresponding std:: versions
  to get the HIP compile working again

- unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h
  Change introduced a recent commit breaks the HIP compile
  (link stage errors out due to failure to inline a function).
  Disabling the recently introduced code (only for HIP compile), to get
  the eigen nightly testing going again.
  Will submit another PR once we have te proper fix.

- Eigen/src/Core/util/ConfigureVectorization.h
  Enabling GPU VECTOR support when HIP compiler is in use
  (for both the host and device compile phases)

unsupported/Eigen/CXX11/src/Tensor/TensorReduction.h

@@ -218,6 +218,7 @@ struct InnerMostDimReducer<Self, Op, false, true> {
   }
 };
 
+#if !defined(EIGEN_HIPCC) 
 template <typename Self, typename Op>
 struct InnerMostDimReducer<Self, Op, true, true> {
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE typename Self::CoeffReturnType
@@ -257,7 +258,8 @@ struct InnerMostDimReducer<Self, Op, true, true> {
     }
   }
 };
-
+#endif
+ 
 template <int DimIndex, typename Self, typename Op, bool vectorizable = (Self::InputPacketAccess && Self::ReducerTraits::PacketAccess)>
 struct InnerMostDimPreserver {
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const Self&, typename Self::Index, Op&, typename Self::PacketReturnType*) {