Add compute model support

[TheLexus]

Hi,

the check for raspberry model version does not work with compute module 4. I added the middle 2 lines to the service:

# Check for RPi model
model=$(cat /proc/cpuinfo | grep 'Model' | awk '{print $5}')
if [ "$model" == "Compute" ]; then
  model=$(cat /proc/cpuinfo | grep 'Model' | awk '{print $7}')
fi
echo "Detected RPi model $model".

Maybe you want add this too.