scsi: aacraid: Rework IOP reset

Reworked IOP reset to remove unneeded variable and created a helper
function to notify fw of an imminent IOP reset.

Signed-off-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com>
Reviewed-by: David Carroll <david.carroll@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>