net/mlx5: Introduce device queue counters

A queue counter can collect several statistics for one or more
hardware queues (QPs, RQs, etc ..) that the counter is attached to.

For Ethernet it will provide an "out of buffer" counter which
collects the number of all packets that are dropped due to lack
of software buffers.

Here we add device commands to alloc/query/dealloc queue counters.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Rana Shahout <ranas@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>