drm/rockchip: vop2: fail cleanly if missing a primary plane for a video-port

In the Linux kernel, the following vulnerability has been resolved: drm/rockchip: vop2: fail cleanly if missing a primary plane for a video-port Each window of a vop2 is usable by a specific set of video ports, so while binding the vop2, we look through the list of available windows trying to find one designated as primary-plane and usable by that specific port. The code later wants to use drm_crtc_init_with_planes with that found primary plane, but nothing has checked so far if a primary plane was actually found. For whatever reason, the rk3576 vp2 does not have a usable primary window (if vp0 is also in use) which brought the issue to light and ended in a null-pointer dereference further down. As we expect a primary-plane to exist for a video-port, add a check at the end of the window-iteration and fail probing if none was found.