When the virtio graphic mode instead of qemu's bochs was used, the
interactive console did not show up because fbdev emulation recently
got disabled.
Reenable fbdev emulation and also add the "simple" and QXL FB DRM
driver to make TTM_HELPER available for the out-of-tree nvidia driver
(which is needed when fbdev emulation is enabled).
Fixes https://github.com/flatcar/Flatcar/issues/1834
Signed-off-by: Kai Lueke <kailuke@microsoft.com>