[RSL] split rsl_rll_push_l3() L3 LV pushign and rsl_rll_push_hdr()

This allows us to generate RSLms messages that have some non-standard
IEs between the RSL/RLL common header and the L3 INFO IE.
diff --git a/src/rsl.c b/src/rsl.c
index c002d33..7bc1712 100644
--- a/src/rsl.c
+++ b/src/rsl.c
@@ -38,6 +38,13 @@
 	dh->ie_link_id = RSL_IE_LINK_IDENT;
 }
 
+void rsl_init_cchan_hdr(struct abis_rsl_cchan_hdr *ch, uint8_t msg_type)
+{
+	ch->c.msg_discr = ABIS_RSL_MDISC_COM_CHAN;
+	ch->c.msg_type = msg_type;
+	ch->ie_chan = RSL_IE_CHAN_NR;
+}
+
 const struct tlv_definition rsl_att_tlvdef = {
 	.def = {
 		[RSL_IE_CHAN_NR]		= { TLV_TYPE_TV },
@@ -277,20 +284,12 @@
 	}
 }
 
-/* Push a RSL RLL header with L3_INFO IE */
-void rsl_rll_push_l3(struct msgb *msg, uint8_t msg_type, uint8_t chan_nr,
-		     uint8_t link_id, int transparent)
+/* Push a RSL RLL header */
+void rsl_rll_push_hdr(struct msgb *msg, uint8_t msg_type, uint8_t chan_nr,
+		      uint8_t link_id, int transparent)
 {
-	uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
 	struct abis_rsl_rll_hdr *rh;
 
-	/* construct a RSLms RLL message (DATA INDICATION, UNIT DATA
-	 * INDICATION) and send it off via RSLms */
-
-	/* Push the L3 IE tag and lengh */
-	msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
-
-	/* Then push the RSL header */
 	rh = (struct abis_rsl_rll_hdr *) msgb_push(msg, sizeof(*rh));
 	rsl_init_rll_hdr(rh, msg_type);
 	if (transparent)
@@ -302,6 +301,22 @@
 	msg->l2h = (uint8_t *)rh;
 }
 
+/* Push a RSL RLL header with L3_INFO IE */
+void rsl_rll_push_l3(struct msgb *msg, uint8_t msg_type, uint8_t chan_nr,
+		     uint8_t link_id, int transparent)
+{
+	uint8_t l3_len = msg->tail - (uint8_t *)msgb_l3(msg);
+
+	/* construct a RSLms RLL message (DATA INDICATION, UNIT DATA
+	 * INDICATION) and send it off via RSLms */
+
+	/* Push the L3 IE tag and lengh */
+	msgb_tv16_push(msg, RSL_IE_L3_INFO, l3_len);
+
+	/* Then push the RSL header */
+	rsl_rll_push_hdr(msg, msg_type, chan_nr, link_id, transparent);
+}
+
 struct msgb *rsl_rll_simple(uint8_t msg_type, uint8_t chan_nr,
 			    uint8_t link_id, int transparent)
 {