[rsl] Send the MultiRateConfig in the RSL Channel Activate msg

If the lchan has AMR as speech codec we also need to send the
multirate config IE in the channel activation. This is already
done for the RSL Channel Modify message.
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 11a4355..10ebd6d 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -650,6 +650,10 @@
 	msgb_tv_put(msg, RSL_IE_MS_POWER, lchan->ms_power);
 	msgb_tv_put(msg, RSL_IE_TIMING_ADVANCE, ta);
 
+	if (lchan->tch_mode == GSM48_CMODE_SPEECH_AMR)
+		msgb_tlv_put(msg, RSL_IE_MR_CONFIG, sizeof(lchan->mr_conf),
+			     (u_int8_t *) &lchan->mr_conf);
+
 	msg->trx = lchan->ts->trx;
 
 	return abis_rsl_sendmsg(msg);