pdch is_enabled: Use API getter instead of accessing field directly

Change-Id: I389f42ef2e95d28643ec51771e46d083d4e20057
diff --git a/src/pcu_l1_if.cpp b/src/pcu_l1_if.cpp
index d0698d9..221a1f7 100644
--- a/src/pcu_l1_if.cpp
+++ b/src/pcu_l1_if.cpp
@@ -540,7 +540,7 @@
 
 	/* Make sure PDCH time-slot is enabled */
 	pdch = &bts->trx[trx].pdch[ts];
-	if (!pdch->m_is_enabled)
+	if (!pdch_is_enabled(pdch))
 		return -EAGAIN;
 
 	/* If there's no TBF attached to this PDCH, we can skip Tx of PTCCH