libubox: update legal info

Reviewed-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
Reviewed-by: Abhimanyu Vishwakarma <Abhimanyu.Vishwakarma@imgtec.com>
Signed-off-by: Rahul Jain <rahul.jain@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libubox/libubox.mk

@@ -6,7 +6,7 @@
 
 LIBUBOX_VERSION = 290c64ef5b5c3e75be851594f269d6a9568e64e5
 LIBUBOX_SITE = git://git.openwrt.org/project/libubox.git
-LIBUBOX_LICENSE = LGPLv2.1, GPLv2, BSD-3c, MIT
+LIBUBOX_LICENSE = ISC, BSD-3c
 LIBUBOX_INSTALL_STAGING = YES
 LIBUBOX_DEPENDENCIES = $(if $(BR2_PACKAGE_JSON_C),json-c)