lscpu not showing number of sockets on arm64

[William Wilson]

When running `lscpu` on arm64, the number of sockets is not populated. This is seen on both Raspberry Pi hardware and in the autopkgtest environment. Example output:

Architecture: aarch64
  CPU op-mode(s): 32-bit, 64-bit
  Byte Order: Little Endian
CPU(s): 4
  On-line CPU(s) list: 0-3
Vendor ID: ARM
  Model name: Cortex-A72
    Model: 3
    Thread(s) per core: 1
    Core(s) per cluster: 4
    Socket(s): -
    Cluster(s): 1
    Stepping: r0p3
    CPU max MHz: 1500.0000
    CPU min MHz: 600.0000
    BogoMIPS: 108.00
    Flags: fp asimd evtstrm crc32 cpuid
Vulnerabilities:
  Itlb multihit: Not affected
  L1tf: Not affected
  Mds: Not affected
  Meltdown: Not affected
  Spec store bypass: Vulnerable
  Spectre v1: Mitigation; __user pointer sanitization
  Spectre v2: Vulnerable
  Srbds: Not affected
  Tsx async abort: Not affected

[Andreas Hasenack (ahasenack)]

I tried a few different arm64 hosts (aws VM, a bare metal in a Canonical MAAS cluster), and lscpu
was behaving just fine there. But confirmed it with the pi4 using current util-linux:

util-linux 2.38.1-4ubuntu1

root@l1-lscpu:~# lscpu|grep Socket
Socket(s): -

root@l1-lscpu:~# cat /proc/cpuinfo
processor : 0
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3

processor : 1
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3

processor : 2
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3

processor : 3
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3

Hardware : BCM2835
Revision : c03112
Serial : 10000000f40b82d7
Model : Raspberry Pi 4 Model B Rev 1.2