lscpu: Read available CPUs max and min frequencies

lscpu: Read available CPUs max and min frequencies

Problem:"lscpu frequency-info" command was always reading CPU0
max and min frequencies. If CPU0 is guarded or offline then it used to
display max and min frequencies as NULL.

This patch will read overall CPU max and min frequencies.

Test Results:

Before Patch:

    #lscpu (CPU0 is guarded/offline)
    Architecture:          ppc64le
    Byte Order:            Little Endian
    CPU(s):                120
    On-line CPU(s) list:   8-127
    Thread(s) per core:    8
    Core(s) per socket:    3
    Socket(s):             4
    NUMA node(s):          4
    Model:                 2.1 (pvr 004b 0201)
    Model name:            POWER8E (raw), altivec supported
    CPU max MHz:           (null)
    CPU min MHz:           (null)
    L1d cache:             64K
    L1i cache:             32K
    L2 cache:              512K
    L3 cache:              8192K
    NUMA node0 CPU(s):     8-31
    NUMA node1 CPU(s):     32-63
    NUMA node16 CPU(s):    64-95
    NUMA node17 CPU(s):    96-127

With Patch:

    # ./lscpu
    Architecture:          ppc64le
    Byte Order:            Little Endian
    CPU(s):                120
    On-line CPU(s) list:   8-127
    Thread(s) per core:    8
    Core(s) per socket:    3
    Socket(s):             4
    NUMA node(s):          4
    Model:                 2.1 (pvr 004b 0201)
    Model name:            POWER8E (raw), altivec supported
    CPU max MHz:           4322.0000
    CPU min MHz:           2061.0000
    L1d cache:             64K
    L1i cache:             32K
    L2 cache:              512K
    L3 cache:              8192K
    NUMA node0 CPU(s):     8-31
    NUMA node1 CPU(s):     32-63
    NUMA node16 CPU(s):    64-95
    NUMA node17 CPU(s):    96-127

[kzak@redhat.com: - cpu_{max,min}_mhz() refactoring]

Signed-off-by: Mamatha Inamdar <mamatha4@linux.vnet.ibm.com>
Signed-off-by: Karel Zak <kzak@redhat.com>