nat: Fix the log message of the code in case of an allocation failure

This wrong log message appears to be the result of copy and paste
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c
index bbbeb03..a1fc035 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c
@@ -309,7 +309,7 @@
 
 	msg = msgb_alloc_headroom(4096, 128, "rlc");
 	if (!msg) {
-		LOGP(DNAT, LOGL_ERROR, "Failed to allocate clear command.\n");
+		LOGP(DNAT, LOGL_ERROR, "Failed to sccp rlc.\n");
 		return;
 	}