net: dsa: vsc73xx: fix reception from VLAN-unaware bridges

Similar to the situation described for sja1105 in commit 1f9fc48
("net: dsa: sja1105: fix reception from VLAN-unaware bridges"), the
vsc73xx driver uses tag_8021q and doesn't need the ds->untag_bridge_pvid
request. In fact, this option breaks packet reception.

The ds->untag_bridge_pvid option strips VLANs from packets received on
VLAN-unaware bridge ports. But those VLANs should already be stripped
by tag_vsc73xx_8021q.c as part of vsc73xx_rcv() - they are not VLANs in
VLAN-unaware mode, but DSA tags. Thus, dsa_software_vlan_untag() tries
to untag a VLAN that doesn't exist, corrupting the packet.

Fixes: 93e4649 ("net: dsa: provide a software untagging function on RX for VLAN-aware bridges")
Tested-by: Pawel Dembicki <paweldembicki@gmail.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patch.msgid.link/20241014153041.1110364-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/vitesse-vsc73xx-core.c

@@ -851,7 +851,6 @@ static int vsc73xx_setup(struct dsa_switch *ds)
 
 	dev_info(vsc->dev, "set up the switch\n");
 
-	ds->untag_bridge_pvid = true;
 	ds->max_num_bridges = DSA_TAG_8021Q_MAX_NUM_BRIDGES;
 	ds->fdb_isolation = true;