gsm0408_test: RA test: include min/max value cases

(Preparation for adding 3-digit MNC)

Change-Id: Ifbc167de0cc039858112677b8d0cd14a2c8af086
diff --git a/tests/gsm0408/gsm0408_test.c b/tests/gsm0408/gsm0408_test.c
index aa6a8be..ad45507 100644
--- a/tests/gsm0408/gsm0408_test.c
+++ b/tests/gsm0408/gsm0408_test.c
@@ -172,6 +172,18 @@
 		.lac = 11,
 		.rac = 89,
 	},
+	{
+		.mcc = 0,
+		.mnc = 0,
+		.lac = 0,
+		.rac = 0,
+	},
+	{
+		.mcc = 999,
+		.mnc = 999,
+		.lac = 65535,
+		.rac = 255,
+	},
 };
 
 static void test_ra_cap(void)