media: venus: fill missing video_device name

This fills missing (forgotten) video device name with
appropriate string so that udev can distinguishes between
decoder and encoder devices.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>