mesh: Add SPDX License Identifier

mesh: Add SPDX License Identifier

This patch adds SPDX License Identifier and removes the license text.

-------------------------------------
       License            COUNT
-------------------------------------
 LGPL-2.1-or-later    :     48

License: LGPL-2.1-or-later
   mesh/mesh-mgmt.h
   mesh/mesh-mgmt.c
   mesh/net-keys.c
   mesh/mesh-io-api.h
   mesh/mesh.h
   mesh/net-keys.h
   mesh/model.h
   mesh/util.h
   mesh/appkey.c
   mesh/cfgmod.h
   mesh/appkey.h
   mesh/prov.h
   mesh/prov-acceptor.c
   mesh/net.c
   mesh/dbus.h
   mesh/friend.h
   mesh/mesh-io-generic.c
   mesh/main.c
   mesh/util.c
   mesh/dbus.c
   mesh/error.h
   mesh/mesh-config-json.c
   mesh/agent.h
   mesh/pb-adv.c
   mesh/crypto.c
   mesh/crypto.h
   mesh/friend.c
   mesh/pb-adv.h
   mesh/provision.h
   mesh/mesh-config.h
   mesh/mesh-io-generic.h
   mesh/agent.c
   mesh/cfgmod-server.c
   mesh/mesh-io.h
   mesh/keyring.h
   mesh/net.h
   mesh/keyring.c
   mesh/mesh-defs.h
   mesh/mesh.c
   mesh/rpl.c
   mesh/manager.c
   mesh/model.c
   mesh/mesh-io.c
   mesh/node.c
   mesh/prov-initiator.c
   mesh/rpl.h
   mesh/node.h
   mesh/manager.h

Change-Id: I5f80a399c16872afdbfff9143e77fabbbc703b9f
Signed-off-by: anuj.bhumiya <anuj.bhumiya@samsung.com>