drm/bridge: imx: Add LDB driver helper support

This patch adds a helper to support LDB drm bridge drivers for
i.MX SoCs.  Helper functions supported by this helper should
implement common logics for all LDB modules embedded in i.MX SoCs.

Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com> # Colibri iMX8X, LT170410-2WHC, LP156WF1
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220611141421.718743-10-victor.liu@nxp.com