Precision 5560 - Fix for Linux audio (ALSA)

In Linux kernels < 5.14.14, the audio quality is bad as ALSA doesn't recognize the internal rear speakers.  Here is the fix:

• Install ALSA Tools to get HDAJackRetask
  sudo apt install alsa-tools
• Force Pulseaudio to not respawn after killing it
  systemctl --user mask pulseaudio.socket
• Kill pulseaudio
  pulseaudio -k
• Run HDAJackRetask
• Choose Realtek ALC289 codec from the dropdown
• Select "Show unconnected pins"
• Override pin 0x17 and assign to "Internal Speaker LFE"
• Click "Apply now"
• Unmask the socket
  systemctl --user unmask pulseaudio.socket
• Start Pulseaudio
  pulseaudio&
• Open Sound Settings.  You should now see "Analog Surround 4.0 Output" and the Fader slider should be active.
• If everything works:
  systemctl --user mask pulseaudio.socket
  pulseaudio -k
• Click "Install boot override"
• Unmask the socket
  systemctl --user unmask pulseaudio.socket
• Reboot