IB/hfi1: Optimize pio cachelines

Move buffers_allocated pcpu pointer to allocator line.

Move hw_free pointer to releaser line.

Fill other holes revealed by pahole.

Reviewed-by: Sebastian Sanchez <sebastian.sanchez@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>