prepare gsm_data.h header file sharing with osmo-bts

This should not introduce any functional changes, it just re-arranges
some definitions in the header file, and introduces the ROLE_BSC
define that we enable for the BSC-specific fields.
diff --git a/openbsc/src/osmo-nitb/bsc_hack.c b/openbsc/src/osmo-nitb/bsc_hack.c
index 2406873..e548a95 100644
--- a/openbsc/src/osmo-nitb/bsc_hack.c
+++ b/openbsc/src/osmo-nitb/bsc_hack.c
@@ -41,6 +41,7 @@
 #include <openbsc/sms_queue.h>
 #include <openbsc/vty.h>
 #include <openbsc/bss.h>
+#include <openbsc/mncc.h>
 
 #include "../../bscconfig.h"