net: sched: make egress_dev flag part of flower offload struct

Since this is specific to flower now, make it part of the flower offload
struct.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>