Make function amr_is_octet_aligned publicly available

it will be used by mgcp_iuup.c in follow-up patch.

Change-Id: Iffaf90c1f713feef0c609a7581a346f5f28141d9
diff --git a/include/osmocom/mgcp/mgcp_codec.h b/include/osmocom/mgcp/mgcp_codec.h
index 97650e4..97e6b8d 100644
--- a/include/osmocom/mgcp/mgcp_codec.h
+++ b/include/osmocom/mgcp/mgcp_codec.h
@@ -17,3 +17,4 @@
 int mgcp_codec_pt_translate(struct mgcp_conn_rtp *conn_src, struct mgcp_conn_rtp *conn_dst, int payload_type);
 const struct mgcp_rtp_codec *mgcp_codec_pt_find_by_subtype_name(struct mgcp_conn_rtp *conn,
 								const char *subtype_name, unsigned int match_nr);
+bool mgcp_codec_amr_is_octet_aligned(const struct mgcp_rtp_codec *codec);