s390/bpf: Zero-extend bpf prog return values and kfunc arguments
In the Linux kernel, the following vulnerability has been resolved:
s390/bpf: Zero-extend bpf prog return values and kfunc arguments
s390x ABI requires callers to zero-extend unsigned arguments and
sign-extend signed arguments, and callees to zero-extend unsigned
return values and sign-extend signed return values.
s390 BPF JIT currently implements only sign extension. Fix this
omission and implement zero extension too.