virito-blk: drop duplicate check

in_num = req->elem.in_num, and req->elem.in_num is
checked in line 489, so the check about in_num variable
is superflous, let's drop it.

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1435138164-11728-1-git-send-email-arei.gonglei@huawei.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>