drm/sun4i: tv: Rename error label

The other error labels in sun4i_tv_bind() are named after the task they
perform (err_disable_clk to call clk_disable_unprepare for example).

However, the err_cleanup_connector is named after the calling site
(drm_connector_init failing) and will actually cleanup the encoder. Let's
rename it to err_cleanup_encoder to be consistent.

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-v2-39-459522d653a7@cerno.tech