PCUIF: fix coding of 'lqual_cb' field in PCUIF_data

This patch fixes BTS_Tests.TC_pcu_data_ind_lqual_cb, which is currently
failing due to incorrect decoding of the 'lqual_cb' field:

  "Link quality -32512 does not match expected value -256"

The COMP attribute is documented in TITAN's reference guide,
see 4-ttcn3_language_extensions.adoc#attributes for more info.

Change-Id: I79b8cd41010f212898fbf39c4c600ace69603e79
Related: OS#5954
diff --git a/library/PCUIF_Types.ttcn b/library/PCUIF_Types.ttcn
index b8bd6e9..b6a1bfa 100644
--- a/library/PCUIF_Types.ttcn
+++ b/library/PCUIF_Types.ttcn
@@ -103,7 +103,10 @@
 	uint16_t	ber10k,
 	int16_t		ta_offs_qbits,
 	int16_t		lqual_cb
-} with { variant (data) "FIELDLENGTH(162), ALIGN(left)" };
+} with {
+	variant (data) "FIELDLENGTH(162), ALIGN(left)"
+	variant (lqual_cb) "COMP(2scompl)"
+};
 
 type record PCUIF_data_cnf {
 	PCUIF_Sapi	sapi,