Allow c++14 for nvcc

[shkarupa-alex]

Description

I've got an error related to c++14 support while building addons v0.15.0 with GPU support above tf 2.7.0

bazel-out/k8-opt/bin/external/local_config_tf/include/tensorflow/core/framework/tensor_types.h(176): error: "auto" is not allowed here

bazel-out/k8-opt/bin/external/local_config_tf/include/tensorflow/core/framework/tensor_types.h(176): error: pack expansion does not make use of any argument packs

bazel-out/k8-opt/bin/external/local_config_tf/include/tensorflow/core/framework/tensor_types.h(177): error: pack expansion does not make use of any argument packs

3 errors detected in the compilation of "tensorflow_addons/custom_ops/seq2seq/cc/kernels/beam_search_ops_gpu.cu.cc".
ERROR: /home/alex/jupyter/build/addons/tensorflow_addons/custom_ops/seq2seq/BUILD:7:18: output 'tensorflow_addons/custom_ops/seq2seq/_objs/_beam_search_ops_gpu/beam_search_ops_gpu.cu.pic.o' was not created
ERROR: /home/alex/jupyter/build/addons/tensorflow_addons/custom_ops/seq2seq/BUILD:7:18: not all outputs were created or valid
Target //:build_pip_pkg failed to build

Fix

Could solve that by changing allowed c++ standards according to https://github.com/tensorflow/tensorflow/blob/v2.7.0/third_party/gpus/crosstool/clang/bin/crosstool_wrapper_driver_is_not_gcc.tpl#L189

Type of change

• Bug fix
• New Tutorial
• Updated or additional documentation
• Additional Testing
• New Activation and the changes conform to the activation contribution guidelines
• New Callback and the changes conform to the callback contribution guidelines
• New Image addition and the changes conform to the image op contribution guidelines
• New Layer and the changes conform to the layer contribution guidelines
• New Loss and the changes conform to the loss contribution guidelines
• New Metric and the changes conform to the metric contribution guidelines
• New Optimizer and the changes conform to the optimizer contribution guidelines
• New RNN Cell and the changes conform to the rnn contribution guidelines
• New Seq2seq addition and the changes conform to the seq2seq contribution guidelines
• New Text addition and the changes conform to the text op contribution guidelines

Checklist:

• I've properly formatted my code according to the guidelines
  • By running Black + Flake8
  • By running pre-commit hooks
• This PR addresses an already submitted issue for TensorFlow Addons
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• This PR contains modifications to C++ custom-ops

How Has This Been Tested?

Build success tested locally

[bhack]

Thanks