gemini: add EOD marker to rootfs images

With 6409b159 ("gemini: switch to 4.14") the EOF marker were dropped
from the rootfs images. Without the marker the rootfs_data partition
can't be created and it isn't possible to permanently store any
configuration changes.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/gemini/image/Makefile

@@ -130,7 +130,8 @@ TARGET_DEVICES += dlink_dns-313
 
 define Device/itian-raidsonic
 	IMAGES := factory.bin
-	IMAGE/factory.bin := append-rootfs | pad-to 6144k | nas4220b-sq201-images $(1)
+	IMAGE/factory.bin := append-rootfs | pad-rootfs | pad-to 6144k | \
+		nas4220b-sq201-images $(1)
 	DEVICE_PACKAGES := $(GEMINI_NAS_PACKAGES)
 endef