ipath,qib: Expose max_sge_rd correctly

Applications must not assume that max_sge and max_sge_rd are the same,
Hence expose max_sge_rd correctly as well.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Acked-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>