If userspace doesn't enable universal planes, then we automatically
add the primary and cursor planes. But for universal userspace there's
no such check (and maybe we only want to give the lessee one plane,
maybe not even the primary one), hence we need to check for the
implied plane.

v2: don't forget setcrtc ioctl.

v3: Still allow disabling of the crtc in SETCRTC.

Cc: stable@vger.kernel.org
Cc: Keith Packard <keithp@keithp.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190228144910.26488-6-daniel.vetter@ffwll.ch