For reference, the config.scm I used was:

(use-modules (gnu) (gnu bootloader u-boot))
(use-service-modules networking ssh desktop)
(use-package-modules bootloaders screen ssh linux)
;;; Note: Maybe better: linux-libre-arm-generic
;;; Note: Novena upstream uses Kernel 3.19
(operating-system
  (host-name "novena")
  (timezone "Europe/Vienna")
  (locale "en_US.utf8")
  (kernel-arguments '("console=ttymxc1,115200"))
  (initrd-modules (cons* "sdhci-esdhc-imx" "ahci_imx" "sd_mod" "i2c-dev" %base-initrd-modules))
  (bootloader (bootloader-configuration
               (bootloader u-boot-novena-bootloader)
               (target "/dev/sda")))
  (file-systems (cons (file-system
                        (device (file-system-label "novena-root"))
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems))
  (packages (append (list screen openssh) %base-packages))
  (services (append (list (service dhcp-client-service-type)
                          (service openssh-service-type)
                          (service elogind-service-type))
                    %base-services)))