drm/rockchip: vop: correct the source size of uv scale factor setting

When the input color format is YUV, we need to do some external scale
for CBCR. Like,
 * In YUV420 data format:
     cbcr_xscale = dst_w / src_w * 2;
     cbcr_yscale = dst_h / src_h * 2;
 * In YUV422 data format:
     cbcr_xscale = dst_w / src_w * 2;
     cbcr_yscale = dst_h / src_h;
 * In YUV444 data format
     cbcr_xscale = dst_w / src_w;
     cbcr_yscale = dst_h / src_h;

Signed-off-by: Yakir Yang <ykk@rock-chips.com>