pahole noted the wasted 4 bytes after s_lock and r_lock.

Move s_flags and r_psn to fill the holes.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>