add docs for bpf_override_return
add docs for bpf_override_return

mcaleavya/bcc,tuxology/bcc,mcaleavya/bcc,brendangregg/bcc,mcaleavya/bcc,tuxology/bcc,brendangregg/bcc,tuxology/bcc,mcaleavya/bcc,tuxology/bcc,iovisor/bcc,tuxology/bcc,brendangregg/bcc,brendangregg/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc,iovisor/bcc,mcaleavya/bcc,iovisor/bcc