lscpu: add SCALMHZ% and "CPU scaling MHz:"

lscpu: add SCALMHZ% and "CPU scaling MHz:"

$ lscpu
...
  Model name:           Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
    CPU family:         6
    Model:              60
    Thread(s) per core: 2
    Core(s) per socket: 4
    Socket(s):          1
    Stepping:           3
    CPU(s) scaling MHz: 61%
    CPU max MHz:        4400.0000
    CPU min MHz:        800.0000
...

$ lscpu -e=CPU,MAXMHZ,MINMHZ,MHZ,SCALMHZ%
CPU    MAXMHZ   MINMHZ      MHZ SCALMHZ%
  0 4400.0000 800.0000 2800.000      64%
  1 4400.0000 800.0000 4000.146      91%
  2 4400.0000 800.0000 2800.000      64%
  3 4400.0000 800.0000 2800.000      64%
  4 4400.0000 800.0000 2800.000      64%
  5 4400.0000 800.0000 4400.000     100%
  6 4400.0000 800.0000  800.000      18%
  7 4400.0000 800.0000 2800.000      64%

Addresses: https://github.com/karelzak/util-linux/issues/1314
Signed-off-by: Karel Zak <kzak@redhat.com>