SGEs that are contiguous needlessly consume driver dependent TX resources.

The lkey validation logic is enhanced to compress the SGE that ends
up in the send wqe when consecutive addresses are detected.

The lkey validation API used to return 1 (success) or 0 (fail).

The return value is now an -errno, 0 (compressed), or 1 (uncompressed).  A
additional argument is added to pass the last SQE for the compression.

Loopback callers always pass a NULL to last_sge since the optimization is
of little benefit in that situation.
Reviewed-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: NBrian Welty <brian.welty@intel.com>
Signed-off-by: NVenkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Signed-off-by: NMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>