vdpa/mlx5: Use auxiliary_device driver data helpers

Use auxiliary_get_drvdata and auxiliary_set_drvdata helpers.

Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20211221235852.323752-5-david.e.box@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>