abis_rsl: Reduce level from notice to debug for measurement reports

It can happen that OpenBSC decides to close the lchan but we
still receive some measurement reports until the BTS has decided
to close the channel.
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 5093d79..7b19d7f 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -938,7 +938,7 @@
 	/* check if this channel is actually active */
 	/* FIXME: maybe this check should be way more generic/centralized */
 	if (msg->lchan->state != LCHAN_S_ACTIVE) {
-		LOGP(DRSL, LOGL_NOTICE, "%s: MEAS RES for inactive channel\n",
+		LOGP(DRSL, LOGL_DEBUG, "%s: MEAS RES for inactive channel\n",
 			gsm_lchan_name(msg->lchan));
 		return 0;
 	}