busybox initramfs: do not use the IMAGE variable

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/busybox/initramfs.mk

@@ -7,7 +7,7 @@ ifeq ($(BR2_PACKAGE_BUSYBOX_INITRAMFS),y)
 
 BUSYBOX_INITRAMFS_DIR:=$(BUSYBOX_DIR)-initramfs
 BR2_INITRAMFS_DIR:=$(BUILD_DIR)/initramfs
-BB_INITRAMFS_TARGET:=$(IMAGE).initramfs_lst
+BB_INITRAMFS_TARGET:=rootfs.initramfs_lst
 
 $(BUSYBOX_INITRAMFS_DIR)/.unpacked: $(DL_DIR)/$(BUSYBOX_SOURCE)
 	rm -rf $(BUILD_DIR)/tmp $(BUSYBOX_INITRAMFS_DIR)