mscsplit: bsc_vty_init(): decouple from global bsc_gsmnet

Add an explicit gsm_network pointer instead of using the bsc_gsmnet global.
This allows passing a gsm_network struct from the main() scope, which helps to
decouple libmsc from libbsc.

Change-Id: I9e2c0d9c18d4cebb5efb71565ad84df2bc2e0251
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
index 3708bc2..706e507 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
@@ -1329,7 +1329,7 @@
 
 
 /* called by the telnet interface... we have our own init above */
-int bsc_vty_init(const struct log_info *cat)
+int bsc_vty_init(const struct log_info *cat, struct gsm_network *network)
 {
 	logging_vty_add_cmds(cat);
 	return 0;