drm/sun4i: tv: Add missing reset assertion

The reset line is deasserted at bind, and asserted if we ever encounter an
error there. However, it's never asserted in unbind which will lead to a
resource unbalance.

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-v2-40-459522d653a7@cerno.tech