mlxsw: spectrum_switchdev: Schedule respin during trans prepare

Since there's no special support for the bridge events, the driver
returns -EOPNOTSUPP, and thus the commit never happens. Therefore
schedule respin during the prepare stage: there's no real difference one
way or another.

This fixes the problem that mirror-to-gretap offload wouldn't adapt to
changes in bridge vlan configuration right away and another notification
would have to arrive for mlxsw to catch up.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>