package/connman: clarify license of client code

While the core connman code is licensed under GPL-2.0, the client code is
GPL-2.0+ for compatibility with readline (which is GPL-3.0+).

Extend the _LICENSE with this info to clarify that linking against
readline is OK licensing wise.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 7d0ee8b4b8b162e010341f63821410100903370d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/connman/connman.mk

@@ -39,6 +39,7 @@ define CONNMAN_INSTALL_INIT_SYSTEMD
 endef
 
 ifeq ($(BR2_PACKAGE_CONNMAN_CLIENT),y)
+CONNMAN_LICENSE += , GPL-2.0+ (client)
 CONNMAN_CONF_OPTS += --enable-client
 CONNMAN_DEPENDENCIES += readline