The BPF helper is moved into system/bpf/include/ and is available
to all BPF programs in the include search path. Make use of it.
Only minor refactor, no functional change.
Bug: 122665156
Change-Id: Ib5b495aff83874d39abe3640fb369b2ff92b3239
Signed-off-by: Joel Fernandes <joelaf@google.com>