drm/bridge: tc358768: Convert to atomic helpers

The tc358768 driver follows the drm_encoder->crtc pointer that is
deprecated and shouldn't be used by atomic drivers.

Fortunately, the atomic hooks provide the drm_atomic_state and we can
access our current CRTC from that, going from the bridge to its encoder,
to its connector, and to its CRTC.

Let's convert this bridge driver to atomic so we can get rid of the
drm_encoder->crtc dereference.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250313-bridge-connector-v6-15-511c54a604fb@kernel.org


Signed-off-by: Maxime Ripard <mripard@kernel.org>