drm/vc4: hvs: Make the HVS bind first

We'll need to have the HVS binding before the HDMI controllers so that
we can check whether the firmware allows to run in 4kp60. Reorder a bit
the component list, and document the current constraints we're aware of.

Acked-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>