nfp: bpf: use a large constant in unresolved branches

To make absolute relocated branches (branches which will be completely
rewritten with br_set_offset()) distinguishable in user space dumps
from normal jumps add a large offset to them.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>