Add support for MOD operation for s390's JIT.

Same as 280050cc "x86 bpf_jit: support MOD operation" for x86 which
adds JIT support for the generic new MOD operation introduced with
b6069a95

 "filter: add MOD operation".

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>