gsm_04_08: add _NUM_CHREQ_T to enum

_NUM_CHREQ_T defines the last element of the enum

Change-Id: Id67ba8de89dd6288e449197438e9e1c5d7f5a134
diff --git a/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index f395b85..522015a 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -1466,6 +1466,7 @@
 	CHREQ_T_RESERVED_IGNORE,
 	CHREQ_T_PDCH_ONE_PHASE,
 	CHREQ_T_PDCH_TWO_PHASE,
+	_NUM_CHREQ_T,
 };
 
 /* Chapter 11.3 */