net/mlx5: Consolidate devlink documentation in devlink/mlx5.rst

net/mlx5: Consolidate devlink documentation in devlink/mlx5.rst

[ Upstream commit b608dd670bb69c89d5074685899d4c1089f57a16 ]

De-duplicate documentation by removing mellanox/mlx5/devlink.rst. Instead,
only use the generic devlink documentation directory to document mlx5
devlink parameters. Avoid providing general devlink tool usage information
in mlx5-specific documentation.

Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Stable-dep-of: 92214be5979c ("net/mlx5e: Update doorbell for port timestamping CQ before the software counter")
Signed-off-by: Sasha Levin <sashal@kernel.org>