net/mlx5: Avoid false positive lockdep warning by adding lock_class_key

Downstream patch will add devcom component which will be locked in
many places. This can lead to a false positive "possible circular
locking dependency" warning by lockdep, on flows which lock more than
one mlx5 devcom component, such as probing ETH aux device.
Hence, add a lock_class_key per mlx5 device.

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>