build: drop UBI EOF marker from images by default

Only add them where they are actually required.
Should help with compatibility issues with stock U-Boot images that
access UBI

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/imx6/image/Makefile

@@ -94,7 +94,6 @@ define Device/ventana
 	kobs-ng
   KERNEL += | boot-overlay
   IMAGES := nand.ubi bootfs.tar.gz
-  UBINIZE_OPTS :=
   UBINIZE_PARTS = boot=$$(KDIR_KERNEL_IMAGE).boot.ubifs=15
   IMAGE/nand.ubi := append-ubi
   IMAGE/bootfs.tar.gz := bootfs.tar.gz | install-dtb