Raspberry: fix hardware check on 64-bit OS

[kiracus]

context

due to the upstream issue raspberrypi/linux#2110, the /proc/cpuinfo on Raspberry 64-bit OS no longer populate the line beginning with hardware, which breaks this repo's assumption.

the fix logic

for 64-bit OS, read /proc/device-tree/compatible instead and get the SOC string for the rpi devices

test

before the fix, with the command si.system()

I get

{
  manufacturer: '',
  model: '',
  version: 'c03111',
  serial: '{omitted}',
  uuid: '',
  sku: '-',
  virtual: false
}

after the fix

I get

{
  manufacturer: 'Raspberry Pi Foundation',
  model: 'Raspberry Pi 4 Model B Rev 1.1',
  version: 'c03111',
  serial: '{omitted}',
  uuid: '',
  sku: '-',
  virtual: false,
  raspberry: {
    manufacturer: 'Sony UK',
    processor: 'BCM2711',
    type: '4B',
    revision: '1.1'
  }
}

this PR should be able to fix #881

[sebhildebrandt]

Hi @kiracus ... I yesterday also published a fix for that (slightly different than your approach) ... Version 5.25.6 ... can you confirm that this also works on your side?