[GSoC] Adding RPi4 support to qemu-system-aarch64

[Afront]

    Hi,
    
    I would like to propose adding RPi4 to the list of supported
    machines for `qemu-system-aarch64` as my GSoC project, but I'm not
    sure if it's a suitable idea for GSoC since it might be too simple.
    In addition, there is already ongoing progress here,
    but the last update is from a year and a half ago, and it is stated not
      complete as "more firmware properties" still have to be
      implemented.

Thanks,

Luke