net/mlx5: Lag, use lag lock

net/mlx5: Lag, use lag lock

Use a lag specific lock instead of depending on external locks to
synchronise the lag creation/destruction.

With this, taking E-Switch mode lock is no longer needed for syncing
lag logic.

Cleanup any dead code that is left over and don't export functions that
aren't used outside the E-Switch core code.

Signed-off-by: Mark Bloch <[email protected]>
Reviewed-by: Maor Gottlieb <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>