Add ICMPv6 ND header length constants. am: 10ff3ebeef am: 7a969bff50

Original change: https://android-review.googlesource.com/c/platform/frameworks/libs/net/+/1737505

Change-Id: Iafb360fe4efa8c52d32f4aa6d1e090f7504cbe78
tree: 34d1aa7a2ca42c43e1dddd9a493c13016df03ac1
  1. staticlibs/