gpu: lontium-lt9611: Fix NULL pointer dereference in lt9611_connector_init()

A NULL check for bridge->encoder shows that it may be NULL, but it
already been dereferenced on all paths leading to the check.
812	if (!bridge->encoder) {

Dereference the pointer bridge->encoder.
810	drm_connector_attach_encoder(&lt9611->connector, bridge->encoder);

Signed-off-by: Zeng Jingxiang <linuszeng@tencent.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220727073119.1578972-1-zengjx95@gmail.com