libbpf: Remove unused field.

relo->processed is set, but not used. Remove it.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210415141817.53136-1-alexei.starovoitov@gmail.com