drm/of: Make drm_of_find_panel_or_bridge() fail when the device is disabled

There's no point searching for a drm_bridge or drm_panel if the OF node
we're pointing has a status property that is not "okay" or "ok". Just
return -ENODEV in this case.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180509130042.9435-4-boris.brezillon@bootlin.com