drm/omap: fix crtc->plane property delegation

Before universal planes we had to have plane specific properties for the
crtc too, as on the hardware level a crtc uses a plane. In other words,
e.g. 'zorder' property was added to both planes and crtcs, and
omap_crtc.c would delegate the property set/get to the primary plane.

However, the delegation was a bit too generic, delegating all property
set/get calls to planes. Thus it's possible to set, say, FB_ID, on a
crtc, which gets redirected to  the primary plane.

This is not standard, and shouldn't be allowed. To keep backward
compatibility, we still need to redirect the properties we supported
earlier for crtcs, namely 'zorder' and 'rotation'.

This patch redirects only the allowed properties from crtcs to planes.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>