mlxsw: spectrum_acl: Put this_is_rollback to rehash context struct

Put the this_is_rollback flag into rehash context struct in preparations
for interrupt/continue of rehash work.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>