bpf: jit: s390 64/32 bits for index in tail call

[Yauheni Kaliuta <yauheni.kaliuta@xxxxxxxxxx>]

Hi!

I have a question about 6651ee070b3124fe9b9db383e3a895a0e4aded65

```
    With this patch a tail call generates the following code on s390x:
    
     if (index >= array->map.max_entries)
             goto out
     000003ff8001c7e4: e31030100016   llgf    %r1,16(%r3)
     000003ff8001c7ea: ec41001fa065   clgrj   %r4,%r1,10,3ff8001c828
```

Do I understand corretly, that it uses 64 bit index value?

"runtime/jit: pass > 32bit index to tail_call"
test_verifier's test fails for me and I see, for example,
/* mov edx, edx */  in the x86 implementation


-- 
WBR,
Yauheni Kaliuta