osmo_rat_type: add OSMO_RAT_EUTRAN_SGS

osmo-msc is about to implement the SGs interface and requires a RAT indicator
for that.

Change-Id: I00588396bfe03feba38ecb0717d584594f0b2b46
diff --git a/include/osmocom/gsm/gsm_utils.h b/include/osmocom/gsm/gsm_utils.h
index 095ac41..7d0beca 100644
--- a/include/osmocom/gsm/gsm_utils.h
+++ b/include/osmocom/gsm/gsm_utils.h
@@ -246,6 +246,7 @@
 	OSMO_RAT_UNKNOWN = 0,
 	OSMO_RAT_GERAN_A,
 	OSMO_RAT_UTRAN_IU,
+	OSMO_RAT_EUTRAN_SGS,
 
 	/* keep this last */
 	OSMO_RAT_COUNT