drm: zte: add interlace mode support

It adds interlace mode support in VOU TIMING_CTRL and channel control
block, so that VOU driver gets ready to support output device in
interlace mode like TV Encoder.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>