common/mlx5: add glue function for domain sync

In rdma-core, the "mlx5dv_dr_domain_sync" function was already
provided. It is used to flush the rule submission queue. The wrapper
function in the glue layer is added for using this.
It only supports DR flows right now the same as domain creating and
destroying functions.

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>