drm/bridge: Fix the stop condition of drm_bridge_chain_pre_enable()

The drm_bridge_chain_pre_enable() is not the proper opposite of
drm_bridge_chain_post_disable(). It continues along the chain to
_before_ the starting bridge. Let's fix that.

Fixes: 05193dc3 ("drm/bridge: Make the bridge chain a double-linked list")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210416153909.v4.1.If62a003f76a2bc4ccc6c53565becc05d2aad4430@changeid