libfdt: fdt_path_offset_namelen: Reject empty paths am: d10c84c4bc am: 9f4834b735 am: e0440b0907 am: 13d00fad64

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/dtc/+/20024811

Change-Id: I320e177a4d92f1a998510dd2e98ee1cc619d3324
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>