drm/vc4: hvs: Support zpos on all planes

Adds the zpos property to all planes, and creates the dlist
by placing the fragments in the correct order based on zpos.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20221207-rpi-hvs-crtc-misc-v1-5-1f8e0770798b@cerno.tech


Signed-off-by: Maxime Ripard <maxime@cerno.tech>