[][MT7988][Fix dm-verity failed due to non-hashed rootfs in factory.bin]

[Description]
Change non-hashed rootfs to hashed rootfs to generate factory.bin

[Release-log]
N/A

Change-Id: I52763717cb11082c7fc99d8b40cd9f39a83ea161
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7428048
diff --git a/target/linux/mediatek/image/mt7988.mk b/target/linux/mediatek/image/mt7988.mk
index 82402da..a9ae167 100644
--- a/target/linux/mediatek/image/mt7988.mk
+++ b/target/linux/mediatek/image/mt7988.mk
@@ -30,7 +30,7 @@
   IMAGE_SIZE := 65536k
   KERNEL_IN_UBI := 1
   IMAGES += factory.bin
-  IMAGE/factory.bin := append-ubi | check-size $$$$(IMAGE_SIZE)
+  IMAGE/factory.bin := append-ubi rootfs=$$$$(IMAGE_ROOTFS)-hashed-$$(firstword $$(DEVICE_DTS)) | check-size $$$$(IMAGE_SIZE)
   IMAGE/sysupgrade.bin := sysupgrade-tar rootfs=$$$$(IMAGE_ROOTFS)-hashed-$$(firstword $$(DEVICE_DTS)) | \
 	append-metadata
   FIT_KEY_DIR := $(TOPDIR)/../../keys