IB/rdmavt: Break rdma_vt main include header file up

Until all functionality is moved over to rdmavt drivers still need to
access a number of fields in data structures that are predominantly
meant to be used by rdmavt. Once these rdmavt_<ibta_object>.h header
files are no longer being touched by drivers their content should be
moved to rdmavt/<ibta_object>.h. While here move a couple #defines
over to more general IB verbs header files because they fit better.

Reviewed-by: Ira Weiny <ira.weiny@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>