BUG/MINOR: quic: Largest RX packet numbers mixing

When we select the next encryption level in qc_treat_rx_pkts() we
must reset the local largest_pn variable if we do not want to reuse its
previous value for this encryption. This bug could only happend during
handshake step and had no visible impact because this variable
is only used during the header protection removal step which hopefully
supports the packet reordering.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index de65b7f..dd1bbbe 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -3598,6 +3598,7 @@
 	if (qel == cur_el) {
 		BUG_ON(qel == next_el);
 		qel = next_el;
+		largest_pn = -1;
 		goto next_tel;
 	}