Simplify TS alloc: avoid TS reassignment

Assign reserved_*_slots only when multislot masks are found to avoid
reassignment and make code easier to follow.

Change-Id: I9b0482f4ea75ead9855cd78e33c8e70d0ccf4484
Related: OS#2282
diff --git a/src/gprs_rlcmac_ts_alloc.cpp b/src/gprs_rlcmac_ts_alloc.cpp
index cd82ca7..c246676 100644
--- a/src/gprs_rlcmac_ts_alloc.cpp
+++ b/src/gprs_rlcmac_ts_alloc.cpp
@@ -770,8 +770,8 @@
 		return -EINVAL;
 	}
 
-	reserved_dl_slots = dl_slots = ms->reserved_dl_slots();
-	reserved_ul_slots = ul_slots = ms->reserved_ul_slots();
+	dl_slots = ms->reserved_dl_slots();
+	ul_slots = ms->reserved_ul_slots();
 	first_common_ts = ms->first_common_ts();
 	trx = ms->current_trx();
 
@@ -800,11 +800,11 @@
 		rc = find_multi_slots(trx, ms->ms_class(), &ul_slots, &dl_slots);
 		if (rc < 0)
 			return rc;
-
-		reserved_dl_slots = dl_slots;
-		reserved_ul_slots = ul_slots;
 	}
 
+	reserved_dl_slots = dl_slots;
+	reserved_ul_slots = ul_slots;
+
 	/* Step 3: Derive the slot set for the current TBF */
 	if (single) {
 		/* Make sure to consider the first common slot only */