net/mlx5: Parallelize vhca event handling

At present, mlx5 driver have a general purpose
event handler which not only handles vhca event
but also many other events. This incurs a huge
bottleneck because the event handler is
implemented by single threaded workqueue and all
events are forced to be handled in serial manner
even though application tries to create multiple
SFs simultaneously.

Introduce a dedicated vhca event handler which
manages SFs parallel creation.

Signed-off-by: Wei Zhang <weizhang@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>