Revert "drm: of: Properly try all possible cases for bridge/panel detection"

Commit '80253168 ("drm: of: Lookup if child node has panel or
bridge")' introduced the ability to describe a panel under a display
controller without having to use a graph to connect the controller to
its single child panel (or bridge).

The implementation of this would find the first non-graph node and
attempt to acquire the related panel or bridge. This prevents cases
where any other child node, such as a aux bus for a DisplayPort
controller, or an opp-table to find the referenced panel.

Commit '67bae5f2 ("drm: of: Properly try all possible cases for
bridge/panel detection")' attempted to solve this problem by not
bypassing the graph reference lookup before attempting to find the panel
or bridge.

While this does solve the case where a proper graph reference is
present, it does not allow the caller to distinguish between a
yet-to-be-probed panel or bridge and the absence of a reference to a
panel.

One such case is a DisplayPort controller that on some boards have an
explicitly described reference to a panel, but on others have a
discoverable DisplayPort display attached (which doesn't need to be
expressed in DeviceTree).

This reverts commit '67bae5f2 ("drm: of: Properly try all possible
cases for bridge/panel detection")', as a step towards reverting commit
'80253168

 ("drm: of: Lookup if child node has panel or bridge")'.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220420231230.58499-1-bjorn.andersson@linaro.org