net/mlx5e: Decouple CQ from priv

Make CQ struct and methods independent of "priv", use more basic
arguments instead.
This will ease the transition to netdev with multiple mdevs.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>