sgsn: introduce f_send_l3() to allow one function for Gb & Iu

f_send_l3() replaces f_send_l3_gmm_llc() to have one function
which sends L3 messages for Iu and Gb at the same time.
This allows to share most of the tests between Iu & Gb.

Change-Id: If47ad2be459ca7b87d9071d9ff020a51821e4433
1 file changed