gsm_08_58: add missing RSL error cause codes

The define constants for the cause codes "BTS not equipped",
"remote transcoder failure" and "notification overflow" are missing.
Lets add them including value strings.

Change-Id: Ic3e936da00bd256bae03867887851f1a4e30e218
diff --git a/src/gsm/rsl.c b/src/gsm/rsl.c
index 5534aa2..cdbdf91 100644
--- a/src/gsm/rsl.c
+++ b/src/gsm/rsl.c
@@ -295,6 +295,9 @@
 	{ RSL_ERR_CCCH_OVERLOAD,	"CCCH Overload" },
 	{ RSL_ERR_ACCH_OVERLOAD,	"ACCH Overload" },
 	{ RSL_ERR_PROCESSOR_OVERLOAD,	"Processor Overload" },
+	{ RSL_ERR_BTS_NOT_EQUIPPED,     "BTS not equipped" },
+	{ RSL_ERR_REMOTE_TRANSC_FAIL,   "Remote Transcoder Failure" },
+	{ RSL_ERR_NOTIFICATION_OVERFL,  "Notification Overflow" },
 	{ RSL_ERR_RES_UNAVAIL,		"Resource not available, unspecified" },
 	{ RSL_ERR_TRANSC_UNAVAIL,	"Transcoding not available" },
 	{ RSL_ERR_SERV_OPT_UNAVAIL,	"Service or Option not available" },