gb: Add functions to access the LL part of the NS-VC objects

Adds the functions gprs_ns_ll_copy() and gprs_ns_ll_clear(). Renames
gprs_ns_format_peer() to gprs_ns_ll_str(). All of these functions
uniformly access the link layer part within the NS-VC objects.

Sponsored-by: On-Waves ehf
diff --git a/tests/gb/gprs_ns_test.c b/tests/gb/gprs_ns_test.c
index c4fc228..1474fd4 100644
--- a/tests/gb/gprs_ns_test.c
+++ b/tests/gb/gprs_ns_test.c
@@ -134,31 +134,31 @@
 	case S_NS_RESET:
 		printf("==> got signal NS_RESET, NS-VC 0x%04x/%s\n",
 		       nssd->nsvc->nsvci,
-		       gprs_ns_format_peer(nssd->nsvc));
+		       gprs_ns_ll_str(nssd->nsvc));
 		break;
 
 	case S_NS_ALIVE_EXP:
 		printf("==> got signal NS_ALIVE_EXP, NS-VC 0x%04x/%s\n",
 		       nssd->nsvc->nsvci,
-		       gprs_ns_format_peer(nssd->nsvc));
+		       gprs_ns_ll_str(nssd->nsvc));
 		break;
 
 	case S_NS_BLOCK:
 		printf("==> got signal NS_BLOCK, NS-VC 0x%04x/%s\n",
 		       nssd->nsvc->nsvci,
-		       gprs_ns_format_peer(nssd->nsvc));
+		       gprs_ns_ll_str(nssd->nsvc));
 		break;
 
 	case S_NS_UNBLOCK:
 		printf("==> got signal NS_UNBLOCK, NS-VC 0x%04x/%s\n",
 		       nssd->nsvc->nsvci,
-		       gprs_ns_format_peer(nssd->nsvc));
+		       gprs_ns_ll_str(nssd->nsvc));
 		break;
 
 	default:
 		printf("==> got signal %d, NS-VC 0x%04x/%s\n", signal,
 		       nssd->nsvc->nsvci,
-		       gprs_ns_format_peer(nssd->nsvc));
+		       gprs_ns_ll_str(nssd->nsvc));
 		break;
 	}