IB/uverbs: Introduce egress flow steering

The egress flag indicates that this flow steering rule is for egress
traffic. The scope of an egress rule is port-wide, meaning all packets
originated from that port, which match the steering rule specification
will be effected by this steering rule's action.

Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>