mlxsw: spectrum_router: Do not unconditionally clear route offload indication

When mlxsw replaces (or deletes) a route it removes the offload
indication from the replaced route. This is problematic for IPv4 routes,
as the offload indication is stored in the fib_info which is usually
shared between multiple routes.

Instead of unconditionally clearing the offload indication, only clear
it if no other route is using the fib_info.

Fixes: 3984d1a8 ("mlxsw: spectrum_router: Provide offload indication using nexthop flags")
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Reported-by: NAlexander Petrovskiy <alexpe@mellanox.com>
Tested-by: NAlexander Petrovskiy <alexpe@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -3794,6 +3794,9 @@ mlxsw_sp_fib4_entry_offload_unset(struct mlxsw_sp_fib_entry *fib_entry)
 	struct mlxsw_sp_nexthop_group *nh_grp = fib_entry->nh_group;
 	int i;
 
+	if (!list_is_singular(&nh_grp->fib_list))
+		return;
+
 	for (i = 0; i < nh_grp->count; i++) {
 		struct mlxsw_sp_nexthop *nh = &nh_grp->nexthops[i];