remove pointless declaration of struct gsm_network

We were passing a NULL pointer of type struct gsm_network * to
ctrl_interface_setup_dynip(). Remove the pointless declaration
of this struct. Also, replace the sgsn_controlif_setup() helper
function with a direct call to ctrl_interface_setup_dynip().
The helper fnuction was just a thin wrapper around the latter.

Change-Id: Ib4151afa5bff01e63b462cca517fb60ac0503759
Related: OS#3356
3 files changed