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)

Eigen/src/Core/util/ConfigureVectorization.h

@@ -379,10 +379,12 @@
   #include <cuda_fp16.h>
 #endif
 
-#if defined(EIGEN_HIP_DEVICE_COMPILE)
-
+#if defined(EIGEN_HIPCC)
   #define EIGEN_VECTORIZE_GPU
   #include <hip/hip_vector_types.h>
+#endif
+
+#if defined(EIGEN_HIP_DEVICE_COMPILE)
 
   #define EIGEN_HAS_HIP_FP16
   #include <hip/hip_fp16.h>