Only instantiate abs kernel templates if needed.

When MLIR generated GPU kernels are used, there is no need to instantiate the
GPU kernels based on Eigen. This would just lead to unused code being linked
in.

PiperOrigin-RevId: 323998013
Change-Id: Ia1a3057f39e5372ae2da15631f0c65a83a2ca0c8

tensorflow/core/kernels/cwise_op_gpu_abs.cu.cc

@@ -19,7 +19,11 @@ limitations under the License.
 
 namespace tensorflow {
 namespace functor {
+#ifdef MLIR_GENERATED_GPU_KERNELS_ENABLED
+DEFINE_UNARY2(abs, complex64, complex128);
+#else
 DEFINE_UNARY6(abs, Eigen::half, float, double, int64, complex64, complex128);
+#endif
 }  // namespace functor
 }  // namespace tensorflow