cleanup: Remove code that is provided by libosmocore now.

libosmocore contains the GSM08.08 definition, no need to copy
that anymore.
diff --git a/src/main.c b/src/main.c
index 0df22a1..8ce1330 100644
--- a/src/main.c
+++ b/src/main.c
@@ -30,12 +30,11 @@
 #include <cellmgr_debug.h>
 
 #include <osmocore/talloc.h>
+#include <osmocore/protocol/gsm_08_08.h>
 
 #include <osmocom/vty/command.h>
 #include <osmocom/vty/vty.h>
 
-#include <openbsc_nat/bssap.h>
-
 #include <sys/stat.h>
 #include <sys/types.h>