goldfish_sensors: hack in minimal support for acceleration

This imports a small chunk of the old hw-sensors code to handle the
acceleration code. The old code "supported" a bunch of different sensors
however I've dropped all the boilerplate for that. Any potential
upstream solution will probably want to enumerate things differently.

Currently this needs to be selected on the command line:

    -device virtio-serial-device \
    -device virt-goldfish-sensors,name=virt-goldfish-sensors