Fix ppc64le compile failure libpng (#19291)

Building Tensorflow on ppc64le fails with the message:
ERROR: /root/tensorflow/tensorflow/cc/BUILD:422:1: Linking of rule
'//tensorflow/cc:ops/control_flow_ops_gen_cc' failed (Exit 1)
bazel-out/host/bin/_solib_local/_U_S_Stensorflow_Scc_Cops_Scontrol_Uflow
_Uops_Ugen_Ucc___Utensorflow/libtensorflow_framework.so:
undefined reference to `png_init_filter_functions_vsx'
collect2: error: ld returned 1 exit status

This is fixed by adding powerpc specific files from the png archive
for @org_tensorflow//tensorflow:linux_ppc64le builds only.