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

While bridge/panel detection was initially relying on the usual
port/ports-based of graph detection, it was recently changed to
perform the lookup on any child node that is not port/ports
instead when such a node is available, with no fallback on the
usual way.

This results in breaking detection when a child node is present
but does not contain any panel or bridge node, even when the
usual port/ports-based of graph is there.

In order to support both situations properly, this commit reworks
the logic to try both options and not just one of the two: it will
only return -EPROBE_DEFER when both have failed.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Fixes: 80253168

 ("drm: of: Lookup if child node has panel or bridge")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220329132732.628474-1-paul.kocialkowski@bootlin.com