Allow USB in BusID
!335 (merged) fixed a similar issue so Option "kmsdev" is also a binding contract to the X server.
!155 (closed) fixed parsing USB BUS IDs but still, the notion of having to use PLATFORM: prefix for a USB device is non-intuitive.
!336 (merged) includes !155 (closed) and expands the BUS types to handle USB: as a BusID prefix. This allows using the USB device path in BusID. Although this is only stable if the USB device is plugged into the same socket, some people may prefer using BusID instead of Option "kmsdev" "/dev/dri/cardN" that depends on driver load order.