drm/connector: Only register TV mode property if present

The drm_create_tv_properties() will create the TV mode property
unconditionally.

However, since we'll gradually phase it out, let's register it only if we
have a list passed as an argument. This will make the transition easier.

Acked-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Acked-in-principle-or-something-like-that-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://lore.kernel.org/r/20220728-rpi-analog-tv-properties-v10-3-256dad125326@cerno.tech


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