IB/rdmavt: Move MR datastructures into rvt

This patch adds the MR datastructures based on hfi1 into rvt. For now the
data structures are defined in include/rdma/rdma_vt.h but once all MR
functionality has been moved from the drivers into rvt these should move to
rdmavt/mr.h

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dean Luick <dean.luick@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>