ns2: Move to one common/shared ns2_bind_alloc()

Avoid code duplication between three different drivers by sharing
the "core" of the bind initialization in a new, shared ns2_bind_alloc().

Change-Id: I535fc68e94fcd695de827dd922706adc1c5a2cb7
diff --git a/src/gb/gprs_ns2_internal.h b/src/gb/gprs_ns2_internal.h
index e149767..4a899ed 100644
--- a/src/gb/gprs_ns2_internal.h
+++ b/src/gb/gprs_ns2_internal.h
@@ -274,6 +274,9 @@
 				 enum gprs_ns2_vc_mode vc_mode,
 				 const char *id);
 
+int ns2_bind_alloc(struct gprs_ns2_inst *nsi, const char *name,
+		   struct gprs_ns2_vc_bind **result);
+
 struct msgb *ns2_msgb_alloc(void);
 
 void ns2_sns_write_vty(struct vty *vty, const struct gprs_ns2_nse *nse);