RDMA/i40iw: Fixes for WQE alignment

Invalidation after every WQE write is changed to invalidate
only if required. NOPs are padded so that WQE writes are
aligned to 64B boundary.

Signed-off-by: Tatyana Nikolova <tatyana.e.nikolova@intel.com>
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>