net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

This improves performance and stability of
DL-3xxx/DL-5xxx/DL-6xxx device series.

Specifically prevents device from temporary network dropouts when
playing video from the web and network traffic going through is high.

Signed-off-by: Dominik Czerwik <dominik.czerwik@synaptics.com>
Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
Link: https://lore.kernel.org/r/20220720060518.541-1-lukasz.spintzyk@synaptics.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>