drm/rockchip: vop: remove hardware cursor window

hardware cursor windows only have some fixed size, and not support
width virtual, when move hardware cursor windows outside of left,
the display would be wrong, so this window can't for cursor now.

And Tag hardware cursor window as a overlay is wrong, will make
userspace wrong behaviour.

So just remove the hardware cursor window

Signed-off-by: Mark Yao <mark.yao@rock-chips.com>