mpt3sas: correct scsi_{target,device} hostdata allocation

mpt3sas: correct scsi_{target,device} hostdata allocation

In _scsih_{slave,target}_alloc, an incorrect structure type is passed
to sizeof() when allocating storage for hostdata.  Luckily larger
structure types were used, so at least the wrong sizes were safe:

  struct scsi_device (1784 bytes) > struct MPT3SAS_DEVICE (24 bytes)
  struct scsi_target (760 bytes)  > struct MPT3SAS_TARGET (32 bytes)

This fixes the following smatch warnings:

  drivers/scsi/mpt3sas/mpt3sas_scsih.c:1166 _scsih_target_alloc()
    warn: struct type mismatch 'MPT3SAS_TARGET vs scsi_target'

  drivers/scsi/mpt3sas/mpt3sas_scsih.c:1280 _scsih_slave_alloc()
    warn: struct type mismatch 'MPT3SAS_DEVICE vs scsi_device'

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>