[SCSI] scsi_debug: Update thin provisioning support

The previous thin provisioning support was not very user friendly
because it depended on all the relevant options being set on the command
line.

Implement support for the Thin Provisioning VPD page from SBC3 r24 and
add module options for TPU (UNMAP) and TPWS (WRITE SAME (16) with UNMAP
bit).  This allows us to have sane default and to enable thin
provisioning with a simple tpu=1 or tpws=1 on the command line depending
on whether we want UNMAP or WRITE SAME behavior.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>