import copy of bpf_net_helpers.h from system/netd/bpf_progs

after this:
  diff system/netd/bpf_progs/bpf_net_helpers.h packages/modules/Connectivity/Tethering/bpf_progs/bpf_net_helpers.h
shows no diff, besides a switch to '#pragma once'
as the include guard.

Test: builds, atest, TreeHugger
Bug: 177884581
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Original-Change: https://android-review.googlesource.com/1733033
Merged-In: Ib943321d46254ba64ce206fb9e3b3414d15e4d45
Change-Id: Ib943321d46254ba64ce206fb9e3b3414d15e4d45
2 files changed