net/mlx5: Refactor LAG peer device lookout bus logic to mlx5 devcom

LAG peer device lookout bus logic required the usage of global lock,
mlx5_intf_mutex.
As part of the effort to remove this global lock, refactor LAG peer
device lookout to use mlx5 devcom layer.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>