drm/rockchip: vop2: use correct destination rectangle height check

The vop2_plane_atomic_check() function incorrectly checks
drm_rect_width(dest) twice instead of verifying both width and height.
Fix the second condition to use drm_rect_height(dest) so that invalid
destination rectangles with height < 4 are correctly rejected.

Fixes: 604be855 ("drm/rockchip: Add VOP2 driver")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20251012142005.660727-1-alok.a.tiwari@oracle.com