drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled

DT nodes might be present in the DT but with a status property set to
"disabled" or "fail". In this case, we should not return -EPROBE_DEFER
when the caller asks for a drm_panel instance. Return -ENODEV instead.

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/20180509130042.9435-3-boris.brezillon@bootlin.com