[SCSI] scsi_debug: fix endianness bug in sdebug_build_parts()

With module parameter num_parts > 0, partition table is built on the
ramdisk storage when loading the driver.  Unfortunately, there is an
endianness bug in sdebug_build_parts().  So the partition table is not
correctly initialized on big-endian systems.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Tested-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>