tizen: Ship only BSD licence from libcoap

tizen: Ship only BSD licence from libcoap

libcoap-4.1.1 is also licenced LICENSE.GPL,
to avoid ambiguity, tizen use the more permissive one, BSD.

This patch can be reverted,
 if Tizen wants to ship all upstream licences

Change-Id: Idc77605c48322f36887cc502dc0be570e2562486
Origin: https://gerrit.iotivity.org/gerrit/#/c/12969/
Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/12805
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>