kbase: sev: Provide more details on virtio-net configuration
kbase: sev: Provide more details on virtio-net configuration

With virtio-net we also need to disable the iPXE option ROM otherwise
a SEV-enabled guest would not boot. While at it, fix the full machine
XML examples accordingly.

Reported-by: Dr. David Alan Gilbert <54dff2264884c355ed5584a3b7f1530b4b26921e@redhat.com>
Signed-off-by: Erik Skultety <2c14d38fa47c8799f1b9c16280abe27f8edfec6e@redhat.com>
Reviewed-by: Laszlo Ersek <7437296077edea1cb64451c122c4dac071f0cfbc@redhat.com>

crobinso/libvirt,jfehlig/libvirt,jardasgit/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,zippy2/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,zippy2/libvirt,olafhering/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt