`gpu_device` option should be able to accept a PCI `vendor_id:product_id` string

[1player]

On multi-GPU computer and on some devices, such as my desktop, the card index used for the gpu_device option is pretty much random. On my system, with only one active GPU and one disabled via kernel cmdline, sometimes my GPU gets index 0, other times has index 1:

% ls -1 /sys/class/drm card1 card1-DP-1 card1-DP-2 card1-DP-3 card1-HDMI-A-1 renderD128 version

Every reboot, I have to check whether the GPU has been loaded with index 0 or 1, and change /etc/gamemode.ini accordingly.

It would be really helpful if the gpu_device option could be set to accept a PCI vendor_id:product_id string to "uniquely" identify a card (example: 1002:73bf for my 6800 XT). It would not be ideal for people with more than one of the same cards, but that's pretty rare.