net/mlx5: Limit non-privileged commands

Limit non-privileged UID commands to half of the available command slots
when privileged UIDs are present.
Privileged throttle commands will not be limited.

Use an xarray to store privileged UIDs. Add insert and remove functions
for privileged UIDs management.

Non-user commands (with uid 0) are not limited.

Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/d2f3dd9a0dbad3c9f2b4bb0723837995e4e06de2.1740574103.git.leon@kernel.org


Signed-off-by: Leon Romanovsky <leon@kernel.org>