Update firmware on Linux

[fractalf]

Hi!

First off, thanks alot for open sourcing the code and keep updating the firmware.

Man that ASID support allowing you to play/remix songs from deepsid is INSANE! I'm blown away by this feature!

Ok, so this is a self-filling feature request, meaning I finally managed to update the firwmare from my Linux machine. I think it would be nice to share this with everyone, and maybe even put it into the manual:

Linux

If you're using Linux, we recommend using amidi to update your TherapSID's firmare. amidi is free and open source CLI utility made by the ALSA project (https://www.alsa-project.org).

Manual:
https://man.archlinux.org/man/extra/alsa-utils/amidi.1.en

Here are the steps to follow:

1. Open up a terminal and navigate to the location where you have stored the firmware update file.
2. Type amidi --list-devices to find the id of your MIDI device (ex: hw:6,0,0)
3. Make sure your TherapSID is in boot-loader mode (turn it on while pressing the filter type button)
4. Type amidi -p <id> -s <file> -i 250 (This last part is important! It's the delay in ms between each SysEx message.)

Example:

$ cd ~/Downloads
$ ls -l        
-rw-r--r-- 1 alf alf 108270 juli   4 09:08 'TherapSID V2.4.syx'

$ amidi --list-devices
Dir Device    Name
IO  hw:6,0,0  MIDI 8x8 MIDI 1

$ amidi -p hw:6,0,0 -s TherapSID\ V2.4.syx -i 250