IB/hfi1: Optimize cachelines for user SDMA request structure

The current user SDMA request structure layout has holes.
The cachelines can be reduced to improve cacheline trading.
Separate fields in the following categories: mostly read,
writable and shared with interrupt.

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