scsi: sg: sg_new_write(): replace access_ok() + __copy_from_user() with copy_from_user()

Link: https://lore.kernel.org/r/20191017193925.25539-2-viro@ZenIV.linux.org.uk


Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>