Provide stepping information for Intel CPU

[anatol]

Here is a cpuinfo data

processor   : 11
vendor_id   : GenuineIntel
cpu family  : 6
model       : 158
model name  : Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
stepping    : 10
microcode   : 0xf0
cpu MHz     : 1259.110
cache size  : 12288 KB
physical id : 0
siblings    : 12
core id     : 5
cpu cores   : 6
apicid      : 11
initial apicid  : 11
fpu     : yes
fpu_exception   : yes
cpuid level : 22
wp      : yes

It looks like cpuid does not provide a way to get the "stepping" information. Would it be possible to add API access to such CPU information?

[klauspost]

Added in #112 - looked into microcode version, but it appears to be privileged and not available through CPUID.