linux-imx

ivshmem-net: fill in and check used descriptor chain len

We are using chains of len==1 make that explicit and expect that from
the remote.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
(cherry picked from commit f958c360044184f58605815d428b83fe4329cafd)