ath79: fix rootfs padding for D-Link DAP-2xxx

It was observed that `rootfs_data` was sometimes not correctly erased
after performing sysupgrade, resulting in previous settings to prevail.

Add call to `wrgg-pad-rootfs` in sysupgrade image recipe to ensure any
previous jffs2 will be wiped, consistent with DAP-2610 from the ipq40xx
target, which introduced the double-flashing procedure for these devices.

Signed-off-by: Sebastian Schaper <[email protected]>

target/linux/ath79/image/generic.mk

@@ -863,7 +863,8 @@ define Device/dlink_dap-2xxx
   IMAGE/factory.img := append-kernel | pad-offset 6144k 160 | \
 	append-rootfs | wrgg-pad-rootfs | mkwrggimg | check-size
   IMAGE/sysupgrade.bin := append-kernel | mkwrggimg | \
-	pad-to $$$$(BLOCKSIZE) | append-rootfs | check-size | append-metadata
+	pad-to $$$$(BLOCKSIZE) | append-rootfs | wrgg-pad-rootfs | \
+	check-size | append-metadata
   KERNEL := kernel-bin | append-dtb | relocate-kernel | lzma
   KERNEL_INITRAMFS := $$(KERNEL) | mkwrggimg
 endef