staging: bcm2835-codec: set device_caps in struct video_device

Instead of filling in the struct v4l2_capability device_caps
field, fill in the struct video_device device_caps field.

That way the V4L2 core knows what the capabilities of the
video device are.

This is similar to a cleanup series by Hans Verkuil [1].

[1] https://www.spinics.net/lists/linux-media/msg153313.html



Signed-off-by: Chen-Yu Tsai <wens@csie.org>