IB/hfi1: Prepare for new HFI1 MSIx API

The current HFI1 MSIx API is difficult to follow, change, or add to.

In anticipation of moving to an more flexible API, move the current
MSIx functionality to the new msix.c module.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Sadanand Warrier <sadanand.warrier@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>