drm/display: add CEC helpers code

Add generic CEC helpers to be used by HDMI drivers. Both notifier and
and adapter are supported for registration. Once registered, the driver
can call common set of functions to update physical address, to
invalidate it or to unregister CEC data. Unlike drm_connector_cec_funcs
(which provides interface common to all implementations, including, but
not limited to the CEC adapter, CEC notifier, CEC pin-based adapter,
etc) the struct drm_connector_hdmi_cec_adapter_ops provides callbacks
specific to the CEC adapter implementations.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250517-drm-hdmi-connector-cec-v6-5-35651db6f19b@oss.qualcomm.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>