IB/rdmavt: Add qp init function

IB/rdmavt: Add qp init function

Add an rvt_qp_init() to initialize specific
common fields as the qp is created or reset.

The routine is shared by the rvt_reset_qp() and
the rvt_create_qp().

The intent is that lock dep assertions will only
appear in the rvt_reset_qp().

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>