vringh: Fix loop descriptors check in the indirect cases

vringh: Fix loop descriptors check in the indirect cases

[ Upstream commit 507bef5c603327aaa5be0d17bdef0ca3d2050593 ]

We should use size of descriptor chain to test loop condition
in the indirect case. And another statistical count is also introduced
for indirect descriptors to avoid conflict with the statistical count
of direct descriptors.

Fixes: a83510ca82bc ("vringh: host-side implementation of virtio rings.")
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Fam Zheng <fam.zheng@bytedance.com>
Message-Id: <20220505100910.137-1-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>