ice: fix setting promisc mode while adding VID filter

There are at least two paths through which VSI promiscuous mode can be
independently configured via ice_fltr_set_vsi_promisc():
- ice_vlan_rx_add_vid() (netdev op)
- ice_service_task() -> ... -> ice_set_promisc()

Both paths may try to program promiscuous mode concurrently. One such
scenario is:

1. Add ice netdev to bond
2. Add the bond netdev to bridge
3. ice netdev enters allmulticast mode (IFF_ALLMULTI)
4. Service task programs promisc mode filter
5. Bridge -> bond calls ice_vlan_rx_add_vid()

Crucially, ice_vlan_rx_add_vid() fails if ice_fltr_set_vsi_promisc()
returns any error, including -EEXIST. This causes VLAN filtering setup
to fail on the bond interface. ice_set_promisc() already handles -EEXIST
correctly.

Fix by adding the same -EEXIST check to ice_vlan_rx_add_vid(): if the
promisc filter is already programmed, continue without returning error.

Fixes: 1273f89578 ("ice: Fix broken IFF_ALLMULTI handling")
Cc: stable@vger.kernel.org
Signed-off-by: Marcin Szycik <marcin.szycik@intel.com>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20260515182419.1597859-4-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/ice/ice_main.c

@@ -3682,7 +3682,7 @@ int ice_vlan_rx_add_vid(struct net_device *netdev, __be16 proto, u16 vid)
 		ret = ice_fltr_set_vsi_promisc(&vsi->back->hw, vsi->idx,
 					       ICE_MCAST_VLAN_PROMISC_BITS,
 					       vid);
-		if (ret)
+		if (ret && ret != -EEXIST)
 			goto finish;
 	}