net: dsa: tag_ocelot_8021q: fix broken reception

The blamed commit changed the dsa_8021q_rcv() calling convention to
accept pre-populated source_port and switch_id arguments. If those are
not available, as in the case of tag_ocelot_8021q, the arguments must be
pre-initialized with -1.

Due to the bug of passing uninitialized arguments in tag_ocelot_8021q,
dsa_8021q_rcv() does not detect that it needs to populate the
source_port and switch_id, and this makes dsa_conduit_find_user() fail,
which leads to packet loss on reception.

Fixes: dcfe767 ("net: dsa: tag_sja1105: absorb logic for not overwriting precise info into dsa_8021q_rcv()")
Signed-off-by: Robert Hodaszi <robert.hodaszi@digi.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241211144741.1415758-1-robert.hodaszi@digi.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: rhodaszi

net/dsa/tag_ocelot_8021q.c

@@ -79,7 +79,7 @@ static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
 static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
 				  struct net_device *netdev)
 {
-	int src_port, switch_id;
+	int src_port = -1, switch_id = -1;
 
 	dsa_8021q_rcv(skb, &src_port, &switch_id, NULL, NULL);