mvebu: omnia: make initramfs image usable out of the box

Currently it's not possible to boot the device with just initramfs image
without additional effort as the initramfs image doesn't contain device
tree.  Fix it by producing FIT based image which could be booted with
following commands:

 setenv bootargs earlyprintk console=ttyS0,115200
 tftpboot ${kernel_addr_r} openwrt-mvebu-cortexa9-cznic_turris-omnia-initramfs-kernel.bin
 bootm ${kernel_addr_r}

Acked-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Reviewed-by: Tomasz Maciej Nowak <tmn505@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/mvebu/image/cortexa9.mk

@@ -32,8 +32,9 @@ define Device/cznic_turris-omnia
   DEVICE_VENDOR := CZ.NIC
   DEVICE_MODEL := Turris Omnia
   KERNEL_INSTALL := 1
+  SOC := armada-385
   KERNEL := kernel-bin
-  KERNEL_INITRAMFS := kernel-bin
+  KERNEL_INITRAMFS := kernel-bin | gzip | fit gzip $$(KDIR)/image-$$(DEVICE_DTS).dtb
   DEVICE_PACKAGES :=  \
     mkf2fs e2fsprogs kmod-fs-vfat kmod-nls-cp437 kmod-nls-iso8859-1 \
     wpad-basic-wolfssl kmod-ath9k kmod-ath10k-ct ath10k-firmware-qca988x-ct \
@@ -42,7 +43,6 @@ define Device/cznic_turris-omnia
   IMAGE/$$(IMAGE_PREFIX)-sysupgrade.img.gz := boot-scr | boot-img | sdcard-img | gzip | append-metadata
   IMAGE/omnia-medkit-$$(IMAGE_PREFIX)-initramfs.tar.gz := omnia-medkit-initramfs | gzip
   IMAGE_NAME = $$(2)
-  SOC := armada-385
   SUPPORTED_DEVICES += armada-385-turris-omnia
   BOOT_SCRIPT := turris-omnia
 endef