disable openssh in rootfs
openssh is enabled in the rootfs build, as is dropbear. I can't think why we might need both other than openssh having scp, sftp, etc.
dropbear supports scp (but not sftp). It provides all the features we need except perhaps privilege separation. For the time being, this seems sufficient and we can remove openssh.
Note: Removing openssh is part of the process of speeding up boot times and integrating a splash screen.