net/mlx4: Add utils for N-Port VFs

This patch adds the following utils:
1. Convert slave_id -> VF
2. Get the active ports by slave_id
3. Convert slave's port to real port
4. Get the slave's port from real port
5. Get all slaves that uses the i'th real port
6. Get all slaves that uses the i'th real port exclusively

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>