net/mlx5: HWS, use lock classes for bwc locks

The HWS BWC API uses one lock per queue and usually acquires one of
them, except when doing changes which require locking all queues in
order. Naturally, lockdep isn't too happy about acquiring the same lock
class multiple times, so inform it that each queue lock is a different
class to avoid false positives.

Fixes: 2ca62599 ("net/mlx5: HWS, added send engine and context handling")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>