apm821xx: fix IB image building

Change the image build code to generate the DTB files as part of the kernel
build phase in order to fix the image build in the ImageBuilder environment.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/linux/apm821xx/image/Makefile

@@ -85,7 +85,7 @@ define Build/create-uImage-dtb
 	-$(STAGING_DIR_HOST)/bin/mkimage -A $(LINUX_KARCH) \
 		-O linux -T kernel -C none \
 		-n '$(call toupper,$(LINUX_KARCH)) LEDE Linux-$(LINUX_VERSION)' \
-		-d $@.dtb $@.new
+		-d $(IMAGE_KERNEL).dtb $@.new
 	@mv $@.new $@
 endef
 
@@ -152,9 +152,9 @@ define Device/WNDR4700
   IMAGE_SIZE:=25559040
   IMAGES := factory.img sysupgrade.tar
   KERNEL_SIZE := 1920k
-  KERNEL := kernel-bin | lzma | uImage lzma | pad-offset $$(BLOCKSIZE) 64 | append-fakerootfs
+  KERNEL := dtb | kernel-bin | lzma | uImage lzma | pad-offset $$(BLOCKSIZE) 64 | append-fakerootfs
   KERNEL_INITRAMFS := kernel-bin | gzip | dtb | wndr4700-specialImage gzip
-  IMAGE/factory.img := dtb | create-uImage-dtb | append-kernel | pad-to 2M | append-ubi | \
+  IMAGE/factory.img := create-uImage-dtb | append-kernel | pad-to 2M | append-ubi | \
 		       netgear-dni | check-size $$$$(IMAGE_SIZE)
   IMAGE/sysupgrade.tar := sysupgrade-tar
   NETGEAR_BOARD_ID := WNDR4700
@@ -178,7 +178,7 @@ define Build/boot-img
 	mkdir -p $@.bootdir/boot
 
 	$(CP) $@.scr $@.bootdir/boot/boot.scr
-	$(CP) $@.dtb $@.bootdir/boot/$(DEVICE_DTB)
+	$(CP) $(IMAGE_KERNEL).dtb $@.bootdir/boot/$(DEVICE_DTB)
 	$(CP) $(IMAGE_KERNEL) $@.bootdir/boot/uImage
 
 	genext2fs --block-size $(BLOCKSIZE) --size-in-blocks $$((1024 * $(BOOT_SIZE))) --root $@.bootdir $@.boot
@@ -211,6 +211,10 @@ define Build/recovery-tar
 		$@
 endef
 
+define Build/export-dtb
+	cp $(IMAGE_KERNEL).dtb $@
+endef
+
 define Device/MyBookLiveDefault
   IMAGE_SIZE := 48m
   BLOCKSIZE := 1024
@@ -220,8 +224,8 @@ define Device/MyBookLiveDefault
   IMAGES := rootfs.img recovery.tar kernel.dtb
   DEVICE_DTB := apollo3g.dtb
   FILESYSTEMS := ext4
-  IMAGE/kernel.dtb := append-dtb
+  IMAGE/kernel.dtb := export-dtb
-  IMAGE/rootfs.img := boot-script | dtb | boot-img | hdd-img
+  IMAGE/rootfs.img := boot-script | boot-img | hdd-img
   IMAGE/recovery.tar := append-rootfs | gzip | uRamdisk | recovery-tar
 endef