MINOR: mux-quic: properly set the flags and name fields

The mux didn't have its flags nor name set, as seen in this output of
"haproxy -vv":

 Available multiplexer protocols :
 (protocols marked as <default> cannot be specified using 'proto' keyword)
   quic : mode=HTTP  side=FE     mux=      flags=
     h2 : mode=HTTP  side=FE|BE  mux=H2    flags=HTX|CLEAN_ABRT|HOL_RISK|NO_UPG

This might have random impacts at certain points like forcing some
connections to close instead of aborting a stream, or not always
handling certain streams as fully HTX-compliant.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 3e32388..786d8bd 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1350,6 +1350,8 @@
 	.subscribe = qc_subscribe,
 	.unsubscribe = qc_unsubscribe,
 	.wake = qc_wake,
+	.flags = MX_FL_CLEAN_ABRT|MX_FL_HTX|MX_FL_NO_UPG,
+	.name = "QUIC",
 };
 
 static struct mux_proto_list mux_proto_quic =