IB/mlx5: Add proper representors support

This commit adds full support for IB representor:

1) Representors profile, We add two new profiles:
   nic_rep_profile - This profile will be used to create an IB device that
   represents the PF/UPLINK.
   rep_profile - This profile will be used to create an IB device that
   represents VFs. Each VF will be its own representor.
2) Proper load/unload callbacks, Those are called by the E-Switch when
   moving to/from switchdev mode.
3) Different flow DB handling for when we in switchdev mode.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>