mvebu: move definition of factory.img out of Device/Default

The Device/Default definition in mvebu defines an IMAGE/factory.img
which is not included in IMAGES, and only used twice in the
individual definitions. Move it out of the default definition
to keep it closer to the reassignment of IMAGES and make it more
consistent with respect to other values of IMAGE/factory.img

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/mvebu/image/Makefile

@@ -104,7 +104,6 @@ define Device/Default
   KERNEL_NAME := zImage
   KERNEL := kernel-bin | append-dtb | uImage none
   IMAGES := sysupgrade.bin
-  IMAGE/factory.img := append-kernel | pad-to $$$$(KERNEL_SIZE) | append-ubi | pad-to $$$$(PAGESIZE)
   IMAGE/sysupgrade.bin := sysupgrade-tar | append-metadata
   SUPPORTED_DEVICES = $(subst _,$(comma),$(1))
   UBINIZE_OPTS := -E 5

target/linux/mvebu/image/cortexa9.mk

@@ -55,6 +55,8 @@ define Device/linksys
   DEVICE_VENDOR := Linksys
   DEVICE_PACKAGES := kmod-mwlwifi wpad-basic
   IMAGES += factory.img
+  IMAGE/factory.img := append-kernel | pad-to $$$$(KERNEL_SIZE) | \
+	append-ubi | pad-to $$$$(PAGESIZE)
   KERNEL_SIZE := 6144k
 endef
 
@@ -151,6 +153,8 @@ define Device/marvell_a385-db-ap
   DEVICE_MODEL := Armada 385 Development Board AP (DB-88F6820-AP)
   DEVICE_DTS := armada-385-db-ap
   IMAGES += factory.img
+  IMAGE/factory.img := append-kernel | pad-to $$$$(KERNEL_SIZE) | \
+	append-ubi | pad-to $$$$(PAGESIZE)
   KERNEL_SIZE := 8192k
   SUPPORTED_DEVICES += armada-385-db-ap
 endef