gsm: Add BTS feature for Osmux

This feature is used by the BTS to signal to the BSC that it supports
using Osmux instead of RTP on the BTS<->BSC(MGW) data plane.

Related: SYS#5987
Change-Id: Ie79bfb6d0a7a8fe2842d2596b3244e7b74a0d5b6
diff --git a/src/gsm/bts_features.c b/src/gsm/bts_features.c
index 88a6fc3..785ad8a 100644
--- a/src/gsm/bts_features.c
+++ b/src/gsm/bts_features.c
@@ -43,6 +43,7 @@
 	{ BTS_FEAT_BCCH_POWER_RED,	"BCCH carrier power reduction mode" },
 	{ BTS_FEAT_DYN_TS_SDCCH8,	"Dynamic Timeslot configuration as SDCCH8" },
 	{ BTS_FEAT_ACCH_TEMP_OVP,	"FACCH/SACCH Temporary overpower" },
+	{ BTS_FEAT_OSMUX,		"Osmux (Osmocom RTP multiplexing)" },
 	{ 0, NULL }
 };