staging/hfi1: add per SDMA engine stats to hfistats

Added the following per sdma engine stats:
  - SendDmaDescFetchedCnt
  - software maintained count of SDMA interrupts
	 (SDmaInt, SDmaIdleInt, SDmaProgressInt)
  - software maintained counts of SDMA error cases

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Vennila Megavannan <vennila.megavannan@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>