drm/atomic: Add atomic_print_state to private objects

A number of drivers (amdgpu, komeda, vc4, etc.) leverage the
drm_private_state structure, but we don't have any infrastructure to
provide debugging like we do for the other components state. Let's add
an atomic_print_state hook to be consistent.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220328124304.2309418-3-maxime@cerno.tech