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/TensorContraction.h

@@ -186,21 +186,21 @@ struct TensorContractionKernel {
       /*ConjugateLhs*/ false, /*ConjugateRhs*/ false>
       GebpKernel;
 
-  EIGEN_DONT_INLINE
+  EIGEN_DEVICE_FUNC EIGEN_DONT_INLINE
   static void packLhs(LhsScalar* lhsBlock,
                       const typename LhsMapper::SubMapper& data_mapper,
                       const StorageIndex depth, const StorageIndex rows) {
     LhsPacker()(lhsBlock, data_mapper, depth, rows, /*stride*/ 0, /*offset*/ 0);
   }
 
-  EIGEN_DONT_INLINE
+  EIGEN_DEVICE_FUNC EIGEN_DONT_INLINE
   static void packRhs(RhsScalar* rhsBlock,
                       const typename RhsMapper::SubMapper& data_mapper,
                       const StorageIndex depth, const StorageIndex cols) {
     RhsPacker()(rhsBlock, data_mapper, depth, cols);
   }
 
-  EIGEN_DONT_INLINE
+  EIGEN_DEVICE_FUNC EIGEN_DONT_INLINE
   static void invoke(const OutputMapper& output_mapper,
                      const LhsScalar* lhsBlock, const RhsScalar* rhsBlock,
                      const StorageIndex rows, const StorageIndex depth,