drm/bridge: Document the probe issue with MIPI-DSI bridges

Interactions between bridges, panels, MIPI-DSI host and the component
framework are not trivial and can lead to probing issues when
implementing a display driver. Let's document the various cases we need
too consider, and the solution to support all the cases.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210910101218.1632297-3-maxime@cerno.tech