seoul: update branch to using vbios emulators

* use seoul branch containing vbios emulator

* report the memory model in the VBE mode info as otherwise the
  Genode framebuffer driver will ignore this mode
seoul: add script turning Genode scenario into VM
ahci: ignore spurious interrupts
debug - use framebuffer scenario of fiasco
debug - disable network backend for seoul-genode
debug - run/env no iommu