nat: Move MSC ip address into the config..

The address can still be specified on the cli and it will
overwrite the config in the config file.
diff --git a/openbsc/src/nat/bsc_nat_vty.c b/openbsc/src/nat/bsc_nat_vty.c
index f0adfaa..a91da7c 100644
--- a/openbsc/src/nat/bsc_nat_vty.c
+++ b/openbsc/src/nat/bsc_nat_vty.c
@@ -55,6 +55,7 @@
 		vty_out(vty, " imsi allow %s%s", _nat->imsi_allow, VTY_NEWLINE);
 	if (_nat->imsi_deny)
 		vty_out(vty, " insi deny %s%s", _nat->imsi_deny, VTY_NEWLINE);
+	vty_out(vty, " msc ip %s%s", _nat->msc_ip, VTY_NEWLINE);
 	return CMD_SUCCESS;
 }
 
@@ -203,6 +204,15 @@
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_nat_msc_ip,
+      cfg_nat_msc_ip_cmd,
+      "msc ip IP",
+      "Set the IP address of the MSC.")
+{
+	bsc_nat_set_msc_ip(_nat, argv[0]);
+	return CMD_SUCCESS;
+}
+
 /* per BSC configuration */
 DEFUN(cfg_bsc, cfg_bsc_cmd, "bsc BSC_NR", "Select a BSC to configure\n")
 {
@@ -316,6 +326,7 @@
 	install_default(NAT_NODE);
 	install_element(NAT_NODE, &cfg_nat_imsi_allow_cmd);
 	install_element(NAT_NODE, &cfg_nat_imsi_deny_cmd);
+	install_element(NAT_NODE, &cfg_nat_msc_ip_cmd);
 
 	/* BSC subgroups */
 	install_element(NAT_NODE, &cfg_bsc_cmd);