IB/mlx5: Break up wqe handling into begin & finish routines
IB/mlx5: Break up wqe handling into begin & finish routines

As a preliminary step for signature feature which will require posting
multiple (3) WQEs for a single WR, we break post_send routine WQE
indexing into begin and finish routines.

This patch does not change any functionality.

Signed-off-by: Sagi Grimberg <380ce2a82d3d08e67ab163b51dc6d30288ad3f13@mellanox.com>
Signed-off-by: Roland Dreier <0d270388f2f92757a5de0f4bd891d3b392c44c4f@purestorage.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs