util: virsysinfo: parse frequency information on S390

util: virsysinfo: parse frequency information on S390

Let's also parse the available processor frequency information on S390
so that it can be utilized by virsh sysinfo:

    # virsh sysinfo

    <sysinfo type='smbios'>
      ...
      <processor>
	<entry name='family'>2964</entry>
	<entry name='manufacturer'>IBM/S390</entry>
	<entry name='version'>00</entry>
	<entry name='max_speed'>5000</entry>
	<entry name='serial_number'>145F07</entry>
      </processor>
      ...
    </sysinfo>

Reviewed-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Signed-off-by: Bjoern Walk <bwalk@linux.vnet.ibm.com>