mgcp_trunk: use enum type for trunk type variable

The trunk_type variable in struct mgcp_trunk is specified as an int,
however there is an enum mgcp_trunk_type specified. Lets use the enum as
type for trunk_type instead of int.

Related: OS#2659
Change-Id: I8e8b0cf448cfe67ad3b7caab24f301708d2a515f
diff --git a/include/osmocom/mgcp/mgcp_trunk.h b/include/osmocom/mgcp/mgcp_trunk.h
index 2bd55e6..c6a0997 100644
--- a/include/osmocom/mgcp/mgcp_trunk.h
+++ b/include/osmocom/mgcp/mgcp_trunk.h
@@ -11,7 +11,7 @@
 	struct mgcp_config *cfg;
 
 	int trunk_nr;
-	int trunk_type;
+	enum mgcp_trunk_type trunk_type;
 
 	char *audio_fmtp_extra;
 	int audio_send_ptime;