Fix bpc to auto default to 10bit

`drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c` L2489



```
	if ((hdmi->colordepth > 8 || hdmi->colordepth == 0) && support_dc)
		color_depth = 10;
	else
		color_depth = 8;
```

Auto default to 10 bit color for supported displays. Defaulting to 8bit kills ability to playback HDR content on wayland hard locking without .dtb modifications