Add IPv6 FragmentHeader struct support am: f8c7d15850

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2988169

Change-Id: I5e48997648b57ade9affae0c6c5b99cc7dc738e9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>