scsi: mpt3sas: Refactor mpt3sas_wait_for_ioc function

No functional change. Doing code refactor of function
mpt3sas_wait_for_ioc() for better readability.

Signed-off-by: Suganath Prabu <suganath-prabu.subramani@broadcom.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>