MINOR: listener: remove the now useless LI_F_QUIC_LISTENER flag

This flag is only used to tag a QUIC listener, which we now know by
its bind_conf's xprt as well. It's only used to decide whether or not
to perform an extra initialization step on the listener. Let's drop it
as well as the flags field.

With the various fields and options moved, the listener struct reduced
by 48 bytes total.
diff --git a/include/haproxy/listener-t.h b/include/haproxy/listener-t.h
index 6e5c423..78c6b9a 100644
--- a/include/haproxy/listener-t.h
+++ b/include/haproxy/listener-t.h
@@ -219,7 +219,6 @@
 	struct listener *li; /* back reference on the listener */
 };
 
-#define LI_F_QUIC_LISTENER       0x00000001  /* listener uses proto quic */
 
 /* The listener will be directly referenced by the fdtab[] which holds its
  * socket. The listener provides the protocol-specific accept() function to
@@ -230,12 +229,11 @@
 	enum li_state state;            /* state: NEW, INIT, ASSIGNED, LISTEN, READY, FULL */
 	/* 2-byte hole here */
 	int luid;			/* listener universally unique ID, used for SNMP */
-	int flags;                      /* LI_F_* flags */
+	int nbconn;			/* current number of connections on this listener */
 	unsigned int thr_idx;           /* thread indexes for queue distribution : (t2<<16)+t1 */
 	__decl_thread(HA_RWLOCK_T lock);
 
 	struct fe_counters *counters;	/* statistics counters */
-	int nbconn;			/* current number of connections on this listener */
 	struct mt_list wait_queue;	/* link element to make the listener wait for something (LI_LIMITED)  */
 	char *name;			/* listener's name */
 
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 664a24a..78b32ee 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -4316,7 +4316,7 @@
 			}
 
 #ifdef USE_QUIC
-			if (listener->flags & LI_F_QUIC_LISTENER) {
+			if (listener->bind_conf->xprt == xprt_get(XPRT_QUIC)) {
 				if (!global.cluster_secret) {
 					diag_no_cluster_secret = 1;
 					if (listener->bind_conf->options & BC_O_QUIC_FORCE_RETRY) {
diff --git a/src/proto_quic.c b/src/proto_quic.c
index 217edd9..9d27553 100644
--- a/src/proto_quic.c
+++ b/src/proto_quic.c
@@ -526,7 +526,6 @@
  */
 static void quic_add_listener(struct protocol *proto, struct listener *listener)
 {
-	listener->flags |= LI_F_QUIC_LISTENER;
 	listener->rx.flags |= RX_F_LOCAL_ACCEPT;
 
 	default_add_listener(proto, listener);