Following X2AP messages were converted to protobuf structures:
* SGNB CHANGE REQUIRED
* SGNB CHANGE CONFIRM
* SGNB CHANGE REFUSE
* SGNB ACTIVITY NOTIFICATION
* GNB STATUS INDICATION
Conversion was based on 3GPP spec 36.423, ver 15.4.0.
Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: Ie75ae5634567347db347967f125d15f0b06a2708