NS: Add missing NS Cause strings

When I added the definitions for the IP-SNS in commit
f030b210e8c13314d361a6b721a0cbcc72935219 back in 2010, I forgot to update
the string definitions in ns_cause_str[].  Let's fix that

Change-Id: I419ccc482d99b01263a60aede83dacd2d9de56ab
diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index 54964d3..976a101 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -365,6 +365,13 @@
 	{ NS_CAUSE_PROTO_ERR_UNSPEC,	"Protocol error, unspecified" },
 	{ NS_CAUSE_INVAL_ESSENT_IE,	"Invalid essential IE" },
 	{ NS_CAUSE_MISSING_ESSENT_IE,	"Missing essential IE" },
+	{ NS_CAUSE_INVAL_NR_IPv4_EP,	"Invalid Number of IPv4 Endpoints" },
+	{ NS_CAUSE_INVAL_NR_IPv6_EP,	"Invalid Number of IPv6 Endpoints" },
+	{ NS_CAUSE_INVAL_NR_NS_VC,	"Invalid Number of NS-VCs" },
+	{ NS_CAUSE_INVAL_WEIGH,		"Invalid Weights" },
+	{ NS_CAUSE_UNKN_IP_EP,		"Unknown IP Endpoint" },
+	{ NS_CAUSE_UNKN_IP_ADDR,	"Unknown IP Address" },
+	{ NS_CAUSE_UNKN_IP_TEST_FAILED,	"IP Test Failed" },
 	{ 0, NULL }
 };