Fix misleading error log

The check is not for an AMR RTP packet. It actually only checks for RTP
header.

Change-Id: I60d7dbfeb2977bcb7102eed19e1c73c9433151a7
diff --git a/src/libosmo-mgcp/mgcp_network.c b/src/libosmo-mgcp/mgcp_network.c
index 3981975..7261b9a 100644
--- a/src/libosmo-mgcp/mgcp_network.c
+++ b/src/libosmo-mgcp/mgcp_network.c
@@ -691,7 +691,7 @@
 {
 	struct rtp_hdr *rtp_hdr;
 	if (msgb_length(msg) < sizeof(struct rtp_hdr)) {
-		LOGPENDP(endp, DRTP, LOGL_ERROR, "AMR RTP packet too short (%d < %zu)\n",
+		LOGPENDP(endp, DRTP, LOGL_ERROR, "RTP packet too short (%d < %zu)\n",
 			 msgb_length(msg), sizeof(struct rtp_hdr));
 		return -EINVAL;
 	}