PCU: fix: actually match IMSI in Packet Paging Request

Change-Id: I0afdd53fd5d2a89e139f65a7aec412a2e12511cc
diff --git a/library/RLCMAC_CSN1_Types.ttcn b/library/RLCMAC_CSN1_Types.ttcn
index 321049c..1bb6232 100644
--- a/library/RLCMAC_CSN1_Types.ttcn
+++ b/library/RLCMAC_CSN1_Types.ttcn
@@ -204,7 +204,10 @@
 		 * uses a byte. */
 		uint4_t			len,
 		octetstring		mobile_id
-	} with { variant (len) "LENGTHTO(mobile_id)" };
+	} with {
+		variant (len) "LENGTHTO(mobile_id)"
+		variant (mobile_id) "BYTEORDER(first)"
+	};
 	type record PageInfoPs {
 		BIT1			presence ('0'B),
 		BIT1			ptmsi_or_mobile_id,