libata: Safely overwrite attached page in WRITE SAME xlat

Safely overwriting the attached page to ATA format from the SCSI formatted
variant.

Signed-off-by: Shaun Tancheff <shaun.tancheff@seagate.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>