Update KVM config

[generic-pers0n]

I recently tested OpenIndiana 2025.10 under KVM, and with the following configuration, it actually works pretty well in my opinion. I therefore have decided to update docs to reflect that right here.

The base configuration used is Generic Linux 2024. You need to make the following modification for OpenIndiana to work:

• Chipset must be i440FX (otherwise neither the hard drive nor the ethernet adapter are detected for some reason)
• Video adapter must be 'vmvga' with the custom XML
• Sound must be AC97 (kept from the previous docs)
• Firmware must be UEFI

Note that I can neither confirm nor deny if xsave instructions play any role. They might if under the legacy BIOS, but apparently under UEFI, they don't matter. Therefore, I decided to remove that mention, but it can be restored if necessary. I also haven't tested sound yet, so I'm keeping the recommendation to use AC97 for now.