scsi: mpt3sas: Fix loop logic

The retry loop continues to iterate until the count reaches 30, even after
receiving the correct value. Exit loop when a non-zero value is read.

Fixes: 4ca10f3e

 ("scsi: mpt3sas: Perform additional retries if doorbell read returns 0")
Cc: stable@vger.kernel.org
Signed-off-by: Ranjan Kumar <ranjan.kumar@broadcom.com>
Link: https://lore.kernel.org/r/20231020105849.6350-1-ranjan.kumar@broadcom.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>