net/mlx5: Expose vnic diagnostic counters for eswitch managed vports

Expose on vport group managers debug counters for their managed vports.

Counters are exposed through debugfs, the directory will be present only
for functions that are eswitch managers and only counters that are
supported on their specific HW/FW will be exposed.

Example:
$ ls /sys/kernel/debug/mlx5/0000:08:00.0/esw/
pf sf_8  vf_0  vf_1

$ ls -l /sys/kernel/debug/mlx5/0000:08:00.0/esw/vf_0/vnic_diag/
cq_overrun
quota_exceeded_command
total_q_under_processor_handle
invalid_command
send_queue_priority_update_flow

List of all counter added:
total_q_under_processor_handle - number of queues in error state due to an
async error or errored command.
send_queue_priority_update_flow - number of QP/SQ priority/SL update
events.
cq_overrun - number of times CQ entered an error state due to an
overflow.
async_eq_overrun -number of time an EQ mapped to async events was
overrun.
comp_eq_overrun - number of time an EQ mapped to completion events was
overrun.
quota_exceeded_command - number of commands issued and failed due to quota
exceeded.
invalid_command - number of commands issued and failed dues to any reason
other than quota exceeded.

Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>