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>