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-nitb/bsc_hack.c b/openbsc/src/osmo-nitb/bsc_hack.c
index 67efe4f..8e1ddae 100644
--- a/openbsc/src/osmo-nitb/bsc_hack.c
+++ b/openbsc/src/osmo-nitb/bsc_hack.c
@@ -271,7 +271,7 @@
 
 	/* This needs to precede handle_options() */
 	vty_init(&vty_info);
-	bsc_vty_init(&log_info);
+	bsc_vty_init(&log_info, bsc_gsmnet);
 	ctrl_vty_init(tall_bsc_ctx);
 
 #ifdef BUILD_SMPP