For the sysmoBTS we want to include a kernel volume inside the UBI as
a fallback in case the mounting of the main kernel is failing. We still
need to modify the boot command of the bootloader to look at this UBI
and to modify the kernel to include the tun/tap modules so the kernel
will be capable of opening a OpenVPN connection.
Currently one needs to write INHERIT += images_types_sysmo into the
conf/local.conf and add ubi-sysmo to the IMAGE_FSTYPES variable.