rlcmac: fix encode_gsm_*(): do not suppress encoding errors

Change-Id: Ieec8e6e0823c6f6985f9d343af6d503b8fe9e6ab
diff --git a/tests/rlcmac/RLCMACTest.ok b/tests/rlcmac/RLCMACTest.ok
index 438417f..27ce879 100644
--- a/tests/rlcmac/RLCMACTest.ok
+++ b/tests/rlcmac/RLCMACTest.ok
@@ -136,7 +136,7 @@
 GPRS multislot class = 3
 EGPRS multislot class = 0
 === Test encoding of MS RA Capability ===
-encode_gsm_ra_cap() returns 0
+encode_gsm_ra_cap() returns -5
 vector1 (len_ind=29) = 13 a5 14 62 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
 vector2 (len_ind=65) = 18 25 14 62 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
 === Test decoding of a malformed vector (short length indicator) ===