net/mlx5: Implement RoCE LAG feature

Available on dual port cards only, this feature keeps
track, using netdev LAG events, of the bonding
and link status of each port's PF netdev.

When both of the card's PF netdevs are enslaved to the
same bond/team master, and only them, LAG state
is active.

During LAG, only one IB device is present for both ports.

In addition to the above, this commit includes FW commands
used for managing the LAG, new facilities for adding and removing
a single device by interface, and port remap functionality according to
bond events.

Please note that this feature is currently used only for mimicking
Ethernet bonding for RoCE - netdevs functionality is not altered,
and their bonding continues to be managed solely by bond/team driver.

Signed-off-by: Aviv Heller <avivh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>