fs/iso9660: fix iso9660 support

Similar to the "fs/initramfs: fix initramfs support" commit the same
problem applies to iso9660 in a different way. By adding iso9660 to
TARGETS it gets called before target-finalize with obvious consequences.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

fs/iso9660/iso9660.mk

@@ -47,5 +47,5 @@ rootfs-iso9660: $(BINARIES_DIR)/rootfs.iso9660
 #
 ################################################################################
 ifeq ($(BR2_TARGET_ROOTFS_ISO9660),y)
-TARGETS += rootfs-iso9660
+TARGETS_ROOTFS += rootfs-iso9660
 endif