scsi: aacraid: Auto detect INTx or MSIx mode during sync cmd processing

During sync command processing, if legacy INTx status indicates command
is not completed, sample the MSIx register and check if it indicates
command completion, set controller MSIx enabled flag.

Signed-off-by: Prasad B Munirathnam <prasad.munirathnam@microsemi.com>
Signed-off-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com>
Reviewed-by: Dave Carroll <david.carroll@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>