Remove obsolete check of conn and lchan pointers not beeing NULL

The check is removed from gsm48_cc_rx_setup() and gsm48_cc_rx_call_conf().
Receiving a layer 3 message implies that the transaction has a subscriber
connection and a logical channel.

This patch fixes the Coverity issues with CID 115311 and CID 1155312.
diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index 54f5f70..0c6b100 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -1803,8 +1803,7 @@
 
 	memset(&setup, 0, sizeof(struct gsm_mncc));
 	setup.callref = trans->callref;
-	if (trans->conn && trans->conn->lchan)
-		setup.lchan_type = trans->conn->lchan->type;
+	setup.lchan_type = trans->conn->lchan->type;
 	tlv_parse(&tp, &gsm48_att_tlvdef, gh->data, payload_len, 0, 0);
 	/* emergency setup is identified by msg_type */
 	if (msg_type == GSM48_MT_CC_EMERG_SETUP)
@@ -1961,8 +1960,7 @@
 
 	memset(&call_conf, 0, sizeof(struct gsm_mncc));
 	call_conf.callref = trans->callref;
-	if (trans->conn && trans->conn->lchan)
-		call_conf.lchan_type = trans->conn->lchan->type;
+	call_conf.lchan_type = trans->conn->lchan->type;
 	tlv_parse(&tp, &gsm48_att_tlvdef, gh->data, payload_len, 0, 0);
 #if 0
 	/* repeat */