net/mlx5: Add a blank line after declarations

There should be a blank lines after declarations.

Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>