scsi: aacraid: remove unused variable managed_request_id

Variable managed_request_id is being assigned but it is never read,
hence it is redundant and can be removed. Cleans up clang warning:

drivers/scsi/aacraid/linit.c:706:5: warning: Value stored to
'managed_request_id' is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>