s390/bpf: Implement unconditional jump with 32-bit offset

Implement the cpuv4 unconditional jump with 32-bit offset, which is
encoded as BPF_JMP32 | BPF_JA and stores the offset in the imm field.
Reuse the existing BPF_JMP | BPF_JA logic.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230919101336.2223655-8-iii@linux.ibm.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>