drm/sun4i: Expand DE2 scaler lib with YUV support

Basic principle of operation when using YUV framebuffer is that chroma
planes have to be upscaled to same size as luma.

Because of that, expand DE2 scaler library to support that.

BSP driver uses another set of FIR filter coefficients for YUV planes.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171201060550.10392-26-jernej.skrabec@siol.net