[SCSI] compat: don't perform unneeded copy in sg_io code

The members from 'status' in struct sg_io_hdr to the last are used to
transfer information from kernel to user space.  The values that user
space sets are just ignored.

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>