drm/rockchip: fix VOP_WIN_GET macro

Commit 9a61c54b ("drm/rockchip: vop: group vop registers") seems to
have unintentionally changed the defintion of this macro.  Since it is
unused, this was not spotted but any attempt to use it results in
compilation errors.

Revert to the previous definition.

Fixes: 9a61c54b

 ("drm/rockchip: vop: group vop registers")
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20190703095111.29117-1-john@metanate.com