Update gsm0808_create_ass() doxygen

* add spec reference
* remove LCLS note: CI parameter is optional but have nothing to do with
  LCLS

It's pretty hard to decipher from the spec what CI is useful for and we
have not used it anyway so let's just keep it as "Optional" for now.

Change-Id: I5552732afcec48047d993ae6ffb73a3e5d7c9202
diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index a84e717..fe7bc2c 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -424,12 +424,12 @@
 	return msg;
 }
 
-/*! Create BSSMAP Assignment Request message
+/*! Create BSSMAP Assignment Request message, 3GPP TS 48.008 §3.2.1.1
  *  \param[in] ct Channel Type
  *  \param[in] cic Circuit Identity Code (Classic A only)
  *  \param[in] ss Socket Address of MSC-side RTP socket (AoIP only)
  *  \param[in] scl Speech Codec List (AoIP only)
- *  \param[in] ci Call Identifier (Optional, LCLS)
+ *  \param[in] ci Call Identifier (Optional), §3.2.2.105
  *  \returns callee-allocated msgb with BSSMAP Assignment Request message */
 struct msgb *gsm0808_create_ass(const struct gsm0808_channel_type *ct,
 				const uint16_t *cic,