libfdt: fdt_path_offset_namelen: Reject empty paths am: d10c84c4bc am: 9f4834b735 am: e0440b0907 am: 13d00fad64 am: 7799b9fb26

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

Change-Id: I77a489de206e6238ac7b5dee2f2edf33d132cdc1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>