gprs_ns2: const the return value of gprs_ns2_ip_vc_sockaddr / gprs_ns2_ip_bind_sockaddr

The sockaddr should not be changed.
free and create the bind/nsvc if the address should be changed.

Change-Id: I371ac2361b569e36722b02fc9cd82ec8da2fa9e3
diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index 50acf99..43a3d77 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -210,8 +210,8 @@
  *  \return pointer to buf on success; NULL on error */
 char *gprs_ns2_ll_str_buf(char *buf, size_t buf_len, struct gprs_ns2_vc *nsvc)
 {
-	struct osmo_sockaddr *local;
-	struct osmo_sockaddr *remote;
+	const struct osmo_sockaddr *local;
+	const struct osmo_sockaddr *remote;
 	struct osmo_sockaddr_str local_str;
 	struct osmo_sockaddr_str remote_str;
 
@@ -847,7 +847,7 @@
 						  const struct osmo_sockaddr *sockaddr)
 {
 	struct gprs_ns2_vc *nsvc;
-	struct osmo_sockaddr *remote;
+	const struct osmo_sockaddr *remote;
 
 	OSMO_ASSERT(nse);
 	OSMO_ASSERT(sockaddr);