net/mlx5: Remove redundant check

If ASO failed in creation, it won't be called to destroy either.
The kernel coding pattern is to make sure that callers are calling
to destroy only for valid objects.

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>