Merge branch 'mlx5-rd-sgl' into rdma.git for-next

From Yamin Friedman:

====================
This series from Yamin implements long standing "TODO" existed in rw.c. It
allows the driver to specify a cut-over point where it is faster to build
a lkey MR rather than do a large SGL for RDMA READ operations.

mlx5 HW gets a notable performane boost by switching to MRs.
====================

Based on the mlx5-next branch from
git://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux for
dependencies

* branch 'mlx5-rd-sgl': (3 commits)
  RDMA/mlx5: Add capability for max sge to get optimized performance
  RDMA/rw: Support threshold for registration vs scattering to local pages
  net/mlx5: Expose optimal performance scatter entries capability