net/mlx5: Use xarray to store and manage completion IRQs

Use xarray to store the completion IRQs instead of a fixed-size allocated
array as not all completion IRQs will be requested on driver load, but
rather on demand when an EQ is created. The xarray offers more scalability,
reduced memory overhead, and provides the ability to dynamically resize the
array when needed.

Signed-off-by: Maher Sanalla <msanalla@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>