Backport the generic DRM HDMI CEC helpers (drm_hdmi_cec_helper and
drm_hdmi_cec_notifier_helper) along with the drm_connector CEC state,
drm_bridge CEC callbacks, and drm_bridge_connector glue that the
adapter registration path requires. Propagate the HDMI physical
address to the CEC adapter from the HDMI state helper hotplug path.
Implement the CEC adapter in dw-hdmi-qp: register definitions, IRQ
handling, transmit and receive paths, logical address programming,
and enable/disable. Pass the named "cec" IRQ and the HDMI reference
clock rate down from dw_hdmi_qp-rockchip so the timer base is
initialised from the actual reference clock.
Enable CONFIG_DRM_DW_HDMI_QP_CEC in tart_defconfig.
