drm/vc4: hdmi: Report that 3d/stereo is allowed

Our HDMI controllers supports Stereo output so let's enable it.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Link: https://lore.kernel.org/r/20220613144800.326124-30-maxime@cerno.tech


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