greybus: camera: Fix size of configure_streams(0)

When APB-A CSI-Tx configuration fails, it is necessary to unconfigure
the camera module issuesing a 0 stream configuration request.
Fix size of request and response to avoid Greybus core complain about
Response size differences.

Testing Done: Triggering the error condition after APB-A CSI-tx
              configuration does not make Greybus core complain anymore

Signed-off-by: Jacopo Mondi <jacopo.mondi@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@linaro.org>
Signed-off-by: Alex Elder <elder@linaro.org>