bsc: change bsc_vty_init to take logging categories as parameter

This change is required to finish the integration of the VTY and
the per-application logging categories that provides:

"vty: integration with logging framework"

in libosmocore.

It has been tested with osmo-nitb. The other just compiled tested.
diff --git a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
index c8d9a62..419c3ed 100644
--- a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
+++ b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
@@ -208,7 +208,7 @@
 
 	vty_info.copyright = openbsc_copyright;
 	vty_init(&vty_info);
-	logging_vty_add_cmds();
+	logging_vty_add_cmds(&log_info);
 	mgcp_vty_init();
 
 	handle_options(argc, argv);