package/freeswitch: Fix added license

Noted by Thomas:
http://lists.busybox.net/pipermail/buildroot/2016-April/158864.html



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
[Thomas: add comma to separate the licenses.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>