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_nat/bsc_nat_vty.c b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
index 786db2d..814d9aa 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
@@ -29,6 +29,7 @@
 #include <osmocore/talloc.h>
 #include <osmocore/rate_ctr.h>
 #include <osmocore/utils.h>
+#include <osmocom/vty/logging.h>
 
 #include <osmocom/sccp/sccp.h>
 
@@ -782,7 +783,8 @@
 
 
 /* called by the telnet interface... we have our own init above */
-int bsc_vty_init(void)
+int bsc_vty_init(const struct log_info *cat)
 {
+	logging_vty_add_cmds(cat);
 	return 0;
 }