IB/mlx5: Expose RSS related capabilities

IB/mlx5: Expose RSS related capabilities

Expose RSS related capabilities on both IB and vendor channels.

In addition to the IB capabilities the driver reports some extra
capabilities on its vendor channel:
- Bit mask of the supported types of hash functions.
- Bit mask of the supported RX fields that can participate
  in the RX hashing.

Those capabilities are applicable only when the link layer
is Ethernet.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>