[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/include/osmocore/rsl.h b/include/osmocore/rsl.h
index 99b90d6..cd84057 100644
--- a/include/osmocore/rsl.h
+++ b/include/osmocore/rsl.h
@@ -7,6 +7,8 @@
 
 void rsl_init_rll_hdr(struct abis_rsl_rll_hdr *dh, uint8_t msg_type);
 
+void rsl_init_cchan_hdr(struct abis_rsl_cchan_hdr *ch, uint8_t msg_type);
+
 extern const struct tlv_definition rsl_att_tlvdef;
 #define rsl_tlv_parse(dec, buf, len)     \
 			tlv_parse(dec, &rsl_att_tlvdef, buf, len, 0, 0)
@@ -22,6 +24,10 @@
 /* Section 3.3.2.3 TS 05.02. I think this looks like a table */
 int rsl_ccch_conf_to_bs_cc_chans(int ccch_conf);
 
+/* 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);
+
 /* 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);