1) For fusion adapters, limit reserved frames for non SCSI commands to 8
   (3 for parallel IOCTLs + 5 for driver's internal DCMDs).
   Earlier reserved commands for non SCSI IO frames was set to 32, so with
   this implementation, increased per controller "can_queue".
   Behavior of MFI controllers will remain unchanged.

2) Optimize the code related to per controller's 'can_queue' setting.
Signed-off-by: NSumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: NChaitra Basappa <chaitra.basappa@avagotech.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>