drm/imx: add internal bridge handling display-timings DT node

i.MX DRM DT bindings allow using either a proper panel / bridge graph to
provide information about connected panels, or just a display-timings DT
node, describing just the timings and the flags. Add helper bridge
driver supporting the latter usecase. It will be used by both LDB and
parallel-display drivers.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # on imx6q-nitrogen6x
Link: https://patchwork.freedesktop.org/patch/msgid/20240602-drm-imx-cleanup-v3-9-e549e2a43100@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>