message: Update Eigen hash for fix of predux bug
  For Maxwell and earlier GPUs, Eigen was incorectly casting fp16 values to
  unsigned int during some reductions. This results in incorrect results in
  Tensorflow's xent and sparse_xent ops when applied to fp16 data.
diff: @@ -95,11 +95,11 @@ def tf_workspace(path_prefix="", tf_repo_name=""):
  tf_http_archive(
  name = "eigen_archive",
  urls = [
  - "https://mirror.bazel.build/bitbucket.org/eigen/eigen/get/429aa5254200.tar.gz",
  - "https://bitbucket.org/eigen/eigen/get/429aa5254200.tar.gz",
  + "https://mirror.bazel.build/bitbucket.org/eigen/eigen/get/b6e6d0cf6a77.tar.gz",
  + "https://bitbucket.org/eigen/eigen/get/b6e6d0cf6a77.tar.gz",
  ],
  - sha256 = "61d8b6fc4279dd1dda986fb1677d15e3d641c07a3ea5abe255790b1f0c0c14e9",
  - strip_prefix = "eigen-eigen-429aa5254200",
  + sha256 = "0840c497f2749b5e90bda666aab96be6da90dc75b4e21ca9843cae69b7fed52a",
  + strip_prefix = "eigen-eigen-b6e6d0cf6a77",
  build_file = str(Label("//third_party:eigen.BUILD")),
  )
  