drm/sun4i: tv: Remove useless destroy function

Our destroy implementation is just calling the generic helper, so let's
just remove our function and directly use the helper.

Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220728-rpi-analog-tv-properties-v2-38-459522d653a7@cerno.tech