i40iw: add connection management code

i40iw_cm.c i40iw_cm.h are used for connection management.

changes since v2:
        Implemented interface changes as reg_phys_mr() is
        not part of inifiniband interface  Done as
        Christoph Hellwig <hch@infradead.org> did for nes.

Changes since v1:
        improved casts
        moved kmap() from i40iw_verbs.c to make them short
        lived.
Acked-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>