ar71xx: add metadata to wpj344 and wpj558 images

This adds metadata to wpj344 and wpj558 images to prevent loading
firmware of wpj344 into wpj558 and vice versa. This until now was
possible and break the units and had to be recovered from the uboot.

Signed-off-by: Enrique Giraldo <enrique.giraldo@galgus.net>

target/linux/ar71xx/image/generic.mk

@@ -874,6 +874,9 @@ define Device/wpj344
   $(Device/wpj-16m)
   DEVICE_TITLE := Compex WPJ344 (16MB flash)
   BOARDNAME := WPJ344
+  SUPPORTED_DEVICES := wpj344
+  IMAGE/sysupgrade.bin := append-kernel | pad-to $$$$(BLOCKSIZE) | \
+	append-rootfs | pad-rootfs | append-metadata | check-size $$$$(IMAGE_SIZE)
 endef
 
 define Device/wpj531
@@ -886,6 +889,9 @@ define Device/wpj558
   $(Device/wpj-16m)
   DEVICE_TITLE := Compex WPJ558 (16MB flash)
   BOARDNAME := WPJ558
+  SUPPORTED_DEVICES := wpj558
+  IMAGE/sysupgrade.bin := append-kernel | pad-to $$$$(BLOCKSIZE) | \
+	append-rootfs | pad-rootfs | append-metadata | check-size $$$$(IMAGE_SIZE)
 endef
 
 define Device/wpj563