s390/bpf: Fix gotol with large offsets

The gotol implementation uses a wrong data type for the offset: it
should be s32, not s16.

Fixes: c690191e

 ("s390/bpf: Implement unconditional jump with 32-bit offset")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20240102193531.3169422-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>