package/batctl: fix license

batman_adv.h and list.h are licensed under MIT

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 5aea15be98be9fc0e9c1e4bc3cd02c1a011cd8c4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/batctl/batctl.mk

@@ -6,7 +6,7 @@
 
 BATCTL_VERSION = 2017.0
 BATCTL_SITE = http://downloads.open-mesh.org/batman/releases/batman-adv-$(BATCTL_VERSION)
-BATCTL_LICENSE = GPL-2.0
+BATCTL_LICENSE = GPL-2.0, MIT (batman_adv.h, list.h)
 BATCTL_DEPENDENCIES = libnl host-pkgconf
 
 define BATCTL_BUILD_CMDS