net: lan966x: Fix IGMP snooping when frames have vlan tag

In case an IGMP frame has a vlan tag, then the function
lan966x_hw_offload couldn't figure out that is a IGMP frame. Therefore
the SW thinks that the frame was already forward by the HW which is not
true.
Extend lan966x_hw_offload to pop the vlan tag if are any and then check
for IGMP frames.

Fixes: 47aeea0d ("net: lan966x: Implement the callback SWITCHDEV_ATTR_ID_BRIDGE_MC_DISABLED ")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

@@ -446,6 +446,12 @@ static bool lan966x_hw_offload(struct lan966x *lan966x, u32 port,
 		     ANA_CPU_FWD_CFG_MLD_REDIR_ENA)))
 		return true;
 
+	if (eth_type_vlan(skb->protocol)) {
+		skb = skb_vlan_untag(skb);
+		if (unlikely(!skb))
+			return false;
+	}
+
 	if (skb->protocol == htons(ETH_P_IP) &&
 	    ip_hdr(skb)->protocol == IPPROTO_IGMP)
 		return false;