Support IBM System z s390 cpu

In IBM System z S390 archtecture,  the /proc/cpuinfo has totally different format with the x86 format. 
It looks like this:

```
# cat /proc/cpuinfo
vendor_id       : IBM/S390
<# processors    : 2
bogomips per cpu: 9328.00
features	: esan3 zarch stfle msa ldisp eimm dfp etf3eh highgprs 
processor 0: version = FF,  identification = 06E276,  machine = 2818
processor 1: version = FF,  identification = 06E276,  machine = 2818
```

So, we need to add additional code to make this s390 cpuinfo be resolved.
I already tested 2 cpus in the s390 cpu context, and in the normal linux test context, based on the example cpuinfo file in the test it already have, I will add one case that it only have cpu 0, no cpu 1 or else.