scsi: megaraid_sas: fix allocate instance->pd_info twice

fix allocate instance->pd_info twice which was introduced by 96188a89

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Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>