gsm0808_utils: Add gsm0808_get_cipher_reject_cause() back with a deprecation notice.

In Change-Id Idf2b99e9ef014eba26e3d4f0f38c2714d3a0520a we accidentially removed this
symbol, let's re-introduce it.

Change-Id: I9fbcbcc6619ef0c63d3682fc86adc80045baab02
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index 6f3c07a..6bf771f 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -1563,6 +1563,11 @@
 	return 0;
 }
 
+int gsm0808_get_cipher_reject_cause(const struct tlv_parsed *tp)
+{
+	return gsm0808_get_cause(tp);
+}
+
 /*! Print a human readable name of the cell identifier to the char buffer.
  * This is useful both for struct gsm0808_cell_id and struct gsm0808_cell_id_list2.
  * See also gsm0808_cell_id_name() and gsm0808_cell_id_list_name().