drm/vc4: Implement atomic_print_state for HVS channel state

The HVS state configuration is useful when debugging what's going on in
the vc4 hardware pipeline. Add an implementation of .atomic_print_state.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220328124304.2309418-5-maxime@cerno.tech