nfp: bpf: don't do ld/mask combination if mask is jump destination

If the mask insn in the ld/mask pair is jump destination, then don't do
combination.

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