gsm: rsl: Define new osmocom extension TLV IE to pass Osmux CID

This is similar to what we already do between BSC<->MSC to pass Osmux
CID (GSM0808_IE_OSMO_OSMUX_CID).
We now want to support Osmux between BSC and Osmocom BTS, hence add an
extension IE which will be used in ipaccess CRCX messages to tell the
BTS to use Osmux.

Change-Id: I580fe99c01bc0a844d877994ec6cd954310e265d
diff --git a/src/gsm/rsl.c b/src/gsm/rsl.c
index 0af366f..3668cea 100644
--- a/src/gsm/rsl.c
+++ b/src/gsm/rsl.c
@@ -125,6 +125,7 @@
 		[RSL_IE_OSMO_REP_ACCH_CAP]	= { TLV_TYPE_TLV },
 		[RSL_IE_OSMO_TRAINING_SEQUENCE]	= { TLV_TYPE_TLV },
 		[RSL_IE_OSMO_TEMP_OVP_ACCH_CAP]	= { TLV_TYPE_TLV },
+		[RSL_IE_OSMO_OSMUX_CID]		= { TLV_TYPE_TLV },
 		[RSL_IE_IPAC_SRTP_CONFIG]	= { TLV_TYPE_TLV },
 		[RSL_IE_IPAC_PROXY_UDP]		= { TLV_TYPE_FIXED, 2 },
 		[RSL_IE_IPAC_BSCMPL_TOUT]	= { TLV_TYPE_TV },